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NBME 15 Answers

Block/Question (14.2 difficulty score)
A 7-year-old boy is brought to the physician ...
Virion releaseπŸ”

Block/Question (11.5 difficulty score)
A healthy 3-year-old boy has a cleft lip and ...
MultifactorialπŸ”

Block/Question (12.7 difficulty score)
Which of the following best explains why ...
Deoxyhemoglobin is a better buffer of hydrogen ions than oxyhemoglobinπŸ”

Block/Question (6.8 difficulty score)
A 9-year-old boy has mild mental retardation ...
Tuberous sclerosisπŸ”

Block/Question (6.4 difficulty score)
A 48-year-old woman comes to the emergency ...
Increased cardiac parasympathetic activityπŸ”

Block/Question (5.7 difficulty score)
A 65-year-old man with a history of ischemic ...
33%πŸ”

Block/Question (10.4 difficulty score)
A 3-year-old girl is brought to the physician ...
Interferon-gamma receptorπŸ”

Block/Question (8.8 difficulty score)
A 4-day-old male newborn who was born at home ...
FirstπŸ”

Block/Question (9.5 difficulty score)
A 75-year-old woman is brought to the ...
Releases NF-ΞΊB after undergoing phosphorylationπŸ”

Block/Question (5.6 difficulty score)
One-half hour after an uncomplicated vaginal ...
OxytocinπŸ”

Block/Question (6.9 difficulty score)
A 36-year-old man who is heterozygous for an ...
LDL receptorπŸ”

Block/Question (5.2 difficulty score)
A 23-year-old woman comes to the physician ...
Oculomotor nerveπŸ”

Block/Question (8.3 difficulty score)
An investigator is designing a study to ...
StratificationπŸ”

Block/Question (8.7 difficulty score)
A 59-year-old man comes to the physician ...
ImatinibπŸ”

Block/Question (8.8 difficulty score)
A 6-year-old boy with severe mental ...
0.2 to 0.5πŸ”

Block/Question (4.5 difficulty score)
A 22-year-old man is brought to the emergency ...
Deep fibular (peroneal)πŸ”

Block/Question (7.8 difficulty score)
A 23-year-old woman comes to the physician ...
GlucokinaseπŸ”

Block/Question (12.8 difficulty score)
A healthy 25-year-old man participates in a ...
epp Amplitude: 1; mepp Amplitude: 1; Response to Ach: 1πŸ”

Block/Question (9.9 difficulty score)
A 2-year-old girl is brought to the emergency ...
AtropineπŸ”

Block/Question (4.3 difficulty score)
A 32-year-old man comes to the physician for ...
Schizoid personality disorderπŸ”

Block/Question (11.9 difficulty score)
A 56-year-old woman comes to the physician ...
Helicobacter pyloriπŸ”

Block/Question (9.4 difficulty score)
A 67-year-old man is brought to the physician ...
Aneurysm of the posterior communicating arteryπŸ”

Block/Question (5.9 difficulty score)
A previously healthy 48-year-old man is ...
Degenerating epithelial cells and dirty brown granular castsπŸ”

Block/Question (8.0 difficulty score)
A 25-year-old woman with a history of ...
Streptococcus mitisπŸ”

Block/Question (8.3 difficulty score)
A 64-year-old man comes to the physician ...
Increased fibrosis in the interstitiumπŸ”

Block/Question (5.0 difficulty score)
A 30-year-old man is brought to the physician ...
Porphobilinogen deaminaseπŸ”

neuro
Block/Question (10.6 difficulty score)
A 43-year-old woman comes to the physician ...
Complex partialπŸ”

Block/Question (7.2 difficulty score)
A 22-year-old woman is found to be HIV ...
Protein processingπŸ”

Block/Question (6.8 difficulty score)
A previous healthy 26-year-old woman comes to ...
Area labeled by letter 'E'πŸ”

Block/Question (14.7 difficulty score)
A 47-year-old man is admitted to the hospital ...
Increased pulmonary capillary pressureπŸ”

Block/Question (8.2 difficulty score)
A 35-year-old woman, gravida 1, para 1, comes ...
Nicotinic acetylcholine receptorπŸ”

Block/Question (11.8 difficulty score)
A 2-month-old male infant is brought to the ...
Glycine receptorπŸ”

Block/Question (7.3 difficulty score)
A 24-year-old woman with Marfan syndrome ...
HypervolemiaπŸ”

Block/Question (4.9 difficulty score)
A 25-year-old primigravid woman at 25 weeks' ...
PrematurityπŸ”

Block/Question (9.0 difficulty score)
A 72-year-old woman is admitted to the ...
Left coronary, circumflex, posterior interventricular (posterior descending)πŸ”

Block/Question (11.4 difficulty score)
A 43-year-old man with a 10-year history of ...
Decreased glutathioneπŸ”

Block/Question (7.5 difficulty score)
A 4-year-old boy is brought to the physician ...
CytoskeletonπŸ”

Block/Question (4.3 difficulty score)
A 45-year-old man comes to the physician for ...
Mitral regurgitationπŸ”

Block/Question (8.4 difficulty score)
A 37-year-old woman is brought to the ...
CardiogenicπŸ”

Block/Question (13.1 difficulty score)
A 3-year-old girl is brought to the physician ...
Abnormal targeting of these enzymes to lysosomesπŸ”

Block/Question (7.5 difficulty score)
A 75-year-old man with chronic obstructive ...
C5aπŸ”

Block/Question (5.8 difficulty score)
A study was begun in the 1950s to determine ...
Cohort studyπŸ”

Block/Question (6.5 difficulty score)
A 56-year-old woman is brought to the ...
LipopolysaccharideπŸ”

Block/Question (6.6 difficulty score)
A 50-year-old man comes to the physician for ...
MedullaryπŸ”

Block/Question (6.9 difficulty score)
A 1-year-old boy is brought to the physician ...
RNA splice errorπŸ”

Block/Question (7.8 difficulty score)
A newborn undergoes surgical repair of ...
EndodermπŸ”

Block/Question (7.4 difficulty score)
A 5-year-old boy is stung on his foot by a ...
Gap formation between endothelial cellsπŸ”

Block/Question (8.4 difficulty score)
A 65-year-old man with hypertension ...
Acid-base: Metabolic alkalosis; Volume contraction: yesπŸ”

Block/Question (8.5 difficulty score)
A 27-year-old man comes to the physician ...
Prolonged fecal excretion of the organismπŸ”

Block/Question (6.9 difficulty score)
A 28-year-old African American man comes to ...
EthnicityπŸ”

Block/Question (11.1 difficulty score)
A 13-year-old boy is scheduled to receive ...
T-lymphocyte thymocytes localized to the thymic cortexπŸ”

Block/Question (9.0 difficulty score)
A 2-month-old girl is brought to the ...
Congenital neutropeniaπŸ”

Block/Question (4.9 difficulty score)
A 42-year-old woman with multiple sclerosis ...
Medial longitudinal fasciculusπŸ”

Block/Question (6.1 difficulty score)
An 18-year-old man is brought to the ...
Inquiry about a history of anabolic steroid useπŸ”

oncology hodgkin lymphoma mutation
Block/Question (5.4 difficulty score)
A 2-month-old boy is brought to the physician ...
PeroxisomesπŸ”

Block/Question (7.3 difficulty score)
A paper says, "We chose the sample size to ...
5%, Type I errorπŸ”

Block/Question (4.2 difficulty score)
A 51-year-old man with a 5-year history of ...
HematuriaπŸ”

pharyngeal_arch digeorge
Block/Question (6.7 difficulty score)
A male newborn is delivered at term with a ...
Third and fourth branchial pouchesπŸ”

Block/Question (7.0 difficulty score)
A 17-year-old boy with chronic renal ...
HydronephrosisπŸ”

Block/Question (7.2 difficulty score)
A newborn delivered at 28 weeks' gestation is ...
Lung elastic recoilπŸ”

Block/Question (8.6 difficulty score)
A 40-year-old woman with breast cancer is ...
Occipital lobeπŸ”

Block/Question (6.3 difficulty score)
A 45-year-old man comes to the physician for ...
Venous return: decreased; Carotid sinus baroreceptor activity: decreased; Cerebral blood flow: decreasedπŸ”

Block/Question (7.2 difficulty score)
A previously healthy 18-year-old woman comes ...
Ξ²-Lactamase productionπŸ”

neuro
Block/Question (7.7 difficulty score)
A 52-year-old man is brought to the physician ...
No constriction because the retinal ganglion cells in the left eye have been destroyedπŸ”

Block/Question (6.2 difficulty score)
A couple has two children with osteogenesis ...
Germline mosaicismπŸ”

Block/Question (7.1 difficulty score)
A 65-year-old woman comes to the physician ...
Osteoblast activity: decreased; Osteoclast activity: increased; RANKL: increasedπŸ”

Block/Question (8.8 difficulty score)
A 45-year-old woman (III,7) comes to the ...
Incomplete penetranceπŸ”

Block/Question (7.3 difficulty score)
A 25-year-old woman comes to the physician ...
Nuclear/retinoid X binding to DNAπŸ”

Block/Question (4.9 difficulty score)
A 70-year-old woman is found dead in her bed ...
HypertrophyπŸ”

Block/Question (8.5 difficulty score)
During a series of normal skeletal muscle ...
ATP is quickly regenerated from creatine phosphateπŸ”

Block/Question (6.8 difficulty score)
A 25-year-old woman comes to the physician ...
ThrombocytopeniaπŸ”

Block/Question (8.0 difficulty score)
An 18-month-old boy with severe combined ...
Irradiated packed red blood cellsπŸ”

Block/Question (8.6 difficulty score)
A 4-year-old boy with a karyotype of 47,XY+21 ...
Excess lymphoblastsπŸ”

Block/Question (6.9 difficulty score)
A 72-year-old woman comes to the physician ...
OsteomalaciaπŸ”

Block/Question (4.3 difficulty score)
A 31-year-old woman is treated for Plasmodium ...
Primaquine kills hypnozoitesπŸ”

Block/Question (7.0 difficulty score)
A study is conducted to evaluate the ...
Lack of blinding between groupsπŸ”

Block/Question (10.1 difficulty score)
An investigator is studying Helicobacter ...
Slipped-strand mispairingπŸ”

Block/Question (6.0 difficulty score)
A previously healthy 26-year-old woman comes ...
External hemorrhoidπŸ”

Block/Question (5.1 difficulty score)
A 22-year-old man comes to the physician ...
Decreased conjugation of bilirubinπŸ”

Block/Question (5.7 difficulty score)
A 72-year-old man comes to the physician ...
Protrusion of the fundus into the chest above the level of T10πŸ”

Block/Question (3.3 difficulty score)
A 1-month old male newborn is brought to the ...
Number of Melanocytes = Normal, Melanosomes = β†“πŸ”

Block/Question (6.9 difficulty score)
A 50-year-old man comes to the emergency ...
AnemiaπŸ”

Block/Question (5.1 difficulty score)
Following a stroke, a 68-year-old man has a ...
H (Wernicke's area)πŸ”

Block/Question (6.1 difficulty score)
Influenza virus strains are characterized by ...
HAπŸ”

Block/Question (4.1 difficulty score)
An investigator conducts a study of the ...
ProteasomeπŸ”

Block/Question (4.4 difficulty score)
A 50-year-old man underwent a bowel resection ...
Hematogenous spread of colonic tumor via the portal venous systemπŸ”

Block/Question (6.8 difficulty score)
A 6-year-old girl is brought to the physician ...
GlutamineπŸ”

Block/Question (2.6 difficulty score)
A 38-year-old man is admitted to the hospital ...
Vitamin K deficiency caused by depletion of the normal gut floraπŸ”

Block/Question (3.0 difficulty score)
A 24-year-old man develops recurrent ...
Sensory neuronsπŸ”

Block/Question (5.6 difficulty score)
A 20-year-old woman comes to the physician ...
The neural plate is present, but the neural tube is not yet completeπŸ”

Block/Question (5.7 difficulty score)
A 30-year-old nulligravid woman comes to the ...
Estrogen in adipose tissueπŸ”

Block/Question (3.7 difficulty score)
A 23-year-old nulligravid woman comes to the ...
Blockage of both fallopian tubesπŸ”

Block/Question (6.1 difficulty score)
A 50-year-old man comes to the physician ...
Stenosis of the right coronary arteryπŸ”

Block/Question (2.8 difficulty score)
A 43-year-old woman is admitted to the ...
HippocampusπŸ”

Block/Question (2.9 difficulty score)
A 45-year-old man with an ulcer in the ...
DiaphragmπŸ”

Block/Question (2.8 difficulty score)
A previously healthy 25-year-old woman comes ...
Germ cellsπŸ”

Block/Question (2.8 difficulty score)
The vaccine against diphtheria confers ...
Purified inactivated toxinπŸ”

Block/Question (2.4 difficulty score)
A 3-year-old girl is brought to the physician ...
DyneinπŸ”

Block/Question (2.5 difficulty score)
A 22-year-old man comes to the emergency ...
MedianπŸ”

Block/Question (4.3 difficulty score)
A 70-year-old man has a 4-month history of ...
Pancreatic enzymesπŸ”

Block/Question (3.5 difficulty score)
A 50-year-old man is brought to the physician ...
"D" label in the image πŸ”

Block/Question (4.2 difficulty score)
A 60-year-old man is brought to the emergency ...
Reversible, dose-dependentπŸ”

Block/Question (3.1 difficulty score)
A 32-year-old man is brought to the emergency ...
pH 7.28, PO2(mmHg) 50, PCO2(mmHg) 60, HCO3-(mEq/L) 27πŸ”

Block/Question (1.8 difficulty score)
A 54-year-old woman comes to the physician ...
This patient's medication has an agonist effect on endometrial estrogen receptorsπŸ”

Block/Question (2.6 difficulty score)
A 45-year-old man with chronic renal failure ...
25-hydroxycholecalciferolπŸ”

Block/Question (3.2 difficulty score)
A 66-year-old woman with ovarian cancer comes ...
Increased tubular hydrostatic pressureπŸ”

Block/Question (3.2 difficulty score)
An 82-year-old woman with alcohol dependence ...
Inadequate hydroxylation of collagen polypeptidesπŸ”

Block/Question (3.5 difficulty score)
A 60-year-old woman develops a secreting ...
Calcium concentration in fecesπŸ”


Block/Question (2.7 difficulty score)
A 13-year-old girl is brought to the ...
TranscriptionπŸ”

Block/Question (2.0 difficulty score)
A 23-year-old primigravid woman develops ...
Listeria monocytogenesπŸ”

Block/Question (3.5 difficulty score)
A male newborn has multiple congenital ...
Absence of adrenal medullaπŸ”

Block/Question (2.1 difficulty score)
The lymphoproliferative properties of the ...
Nasopharyngeal carcinomaπŸ”

Block/Question (3.0 difficulty score)
A 30-year-old woman comes to the physician ...
SerotoninπŸ”

Block/Question (4.0 difficulty score)
A 3-year-old boy with chronic otitis media is ...
Low blood solubilityπŸ”

Block/Question (3.9 difficulty score)
A previously healthy 35-year-old woman ...
PO2 50, PCO2 80, (A-a)O2 10πŸ”

Block/Question (4.1 difficulty score)
A 45-year-old man has a 2-day history of ...
Action of pancreatic enzymes on adiposeπŸ”

Block/Question (2.7 difficulty score)
During an experiment of muscle contraction, ...
Myosin bonding sites on actin remain covered by troponin CπŸ”

Block/Question (1.8 difficulty score)
A 14-year-old boy has fatigue, intermittent ...
Vitamin B12 (cobalmin)πŸ”

Block/Question (2.5 difficulty score)
A 21-year-old woman at 30 weeks' gestation is ...
CyclooxygenaseπŸ”

Block/Question (4.8 difficulty score)
A 56-year-old woman is brought to the ...
1000πŸ”

Block/Question (2.7 difficulty score)
A 32-year-old woman comes to the physician ...
Collecting ductπŸ”

Block/Question (2.5 difficulty score)
A 48-year-old woman comes to the physician ...
Autoantibody (IgM) reactive with IgGπŸ”

Block/Question (3.1 difficulty score)
A 32-year-old woman comes to the physician ...
Internal iliacπŸ”

Block/Question (2.3 difficulty score)
A 53-year-old man develops a fever and ...
Clostridium perfringensπŸ”

Block/Question (1.9 difficulty score)
A 4-year-old boy has respiratory tract ...
Autosomal recessiveπŸ”

Block/Question (2.7 difficulty score)
A previously healthy 27-year-old woman is ...
Superantigen activation of T lymphocytesπŸ”

Block/Question (2.5 difficulty score)
A 50-year-old woman comes to the physician ...
EndothelinπŸ”

Block/Question (5.2 difficulty score)
A 55-year-old man comes to the physician ...
Motor fibers from the vagus nerveπŸ”

Block/Question (3.0 difficulty score)
An 18-year-old man comes to the physician ...
ProlactinπŸ”

Block/Question (2.5 difficulty score)
A 69-year-old woman is brought to the ...
Normal pressure hydrocephalusπŸ”

Block/Question (2.8 difficulty score)
A 7-month-old girl is brought to the ...
Coarctation of the aortaπŸ”

Block/Question (2.6 difficulty score)
A 71-year-old woman is brought to the ...
Temporal arteritisπŸ”

Block/Question (2.1 difficulty score)
A 10-year-old girl with sickle cell disease ...
SalmonellaπŸ”

Heme
Block/Question (2.2 difficulty score)
A 62-year-old woman comes to the physician ...
Multiple myelomaπŸ”

Block/Question (4.2 difficulty score)
A 75-year-old woman comes to the physician ...
Lentigo malignaπŸ”

Block/Question (3.5 difficulty score)
A 27-year-old woman comes to the physician ...
Dilated cardiomyopathyπŸ”

Block/Question (4.0 difficulty score)
A 72-year-old man with poorly controlled ...
Decreased femoral pulsesπŸ”

Block/Question (3.2 difficulty score)
A 17-year-old boy comes to the physician ...
Tuberculosis abscess of the spineπŸ”

Block/Question (3.6 difficulty score)
A food handler has a fresh furuncle on his ...
VomitingπŸ”

Block/Question (2.9 difficulty score)
A 15-year-old is brought to the physician ...
Avascular necrosis of the proximal scaphoid boneπŸ”

Block/Question (5.2 difficulty score)
An investigator who wishes to test the ...
ImmunohistochemistryπŸ”

Block/Question (4.6 difficulty score)
A 67-year-old man comes to the physician ...
BurningπŸ”

Block/Question (4.6 difficulty score)
A 54-year-old man comes to the physician ...
Major depressive disorderπŸ”

Block/Question (2.4 difficulty score)
A 23-year-old woman is brought to the ...
HeroinπŸ”

Block/Question (3.0 difficulty score)
A 43-year-old man comes to the physician ...
Inherited protease deficiencyπŸ”

Block/Question (2.2 difficulty score)
An 8-year-old boy with moderate mental ...
Prader-Willi syndromeπŸ”

Block/Question (3.3 difficulty score)
A 3-year-old girl is brought to the physician ...
Thyroid folliclesπŸ”

Block/Question (2.7 difficulty score)
A 25-year-old primigravid woman at 12 weeks' ...
Partial hyatidiform moleπŸ”

Block/Question (3.0 difficulty score)
A 42-year-old woman comes to the physician ...
Beta-thalassemia minorπŸ”

Block/Question (3.0 difficulty score)
A 19-year-old woman is brought to the ...
OlanzapineπŸ”

Block/Question (2.5 difficulty score)
A 51-year-old woman undergoes dilation and ...
SuccinylcholineπŸ”

Block/Question (4.2 difficulty score)
A 35-year-old metal worker collapses after ...
Amyl nitriteπŸ”

Block/Question (3.5 difficulty score)
A 69-year-old man with benign prostatic ...
BethanecholπŸ”

Block/Question (3.4 difficulty score)
A 34-year-old woman who is a scientist is ...
Potassium iodideπŸ”

Block/Question (2.2 difficulty score)
A 19-year-old woman comes to the physician ...
DoxycyclineπŸ”

Block/Question (2.4 difficulty score)
A study is conducted to assess a new prenatal ...
99%πŸ”

Block/Question (2.6 difficulty score)
A study is conducted of patients with ...
Increased body fat is associated with lower lung capacityπŸ”

Block/Question (3.1 difficulty score)
Vision screening is performed on 4000 people ...
Unable to calculate due to insufficient dataπŸ”

aspirin
Block/Question (2.9 difficulty score)
An 18-year-old woman is brought to the ...
Bleeding timeπŸ”

Block/Question (2.4 difficulty score)
A 28-year-old woman is brought to the ...
Determine the C-peptide concentration in the latest blood specimen drawnπŸ”

Block/Question (3.9 difficulty score)
A 32-year-old man has a 3-month history of ...
Decreased smokingπŸ”

Block/Question (3.7 difficulty score)
A 55 year old woman with colon cancer and a ...
ApoptosisπŸ”

reproductive
Block/Question (2.0 difficulty score)
A 26 year old woman comes to the physician ...
oral metronidazoleπŸ”


Block/Question (2.5 difficulty score)
A 24-year-old woman is admitted to the ...
Ectopic pregnancyπŸ”

Block/Question (1.0 difficulty score)
A 62-year-old man comes to the physician ...
MacrophagesπŸ”

Repro
Block/Question (0.9 difficulty score)
A 62-year-old man undergoes cystoscopy for ...
Ureteric orificesπŸ”

Block/Question (0.6 difficulty score)
A 21-year-old man is brought to the emergency ...
Antisocial πŸ”

Block/Question (0.6 difficulty score)
A 55-year-old woman comes to the physician because
SupraspinatusπŸ”

Block/Question (0.3 difficulty score)
A 10 month old boy has an abdominal mass,10cm ...
Nephroblastoma (Wilms Tumor)πŸ”

Block/Question (0.2 difficulty score)
Four days following a hike in forest,lesion ...
Delayed type 4 HSY reactionπŸ”

Recent comments ...

... andro made a comment on nbme15/block3/q#30 (13 yo boy, receiving chemotherapy for leukemia)
 +13 
submitted by andro(170)

First question : They tell us its a lymphocytic leukemia

Second question : Deciphering whether it is a B cell or T cell.

The cells have no surface bound Ig M ,Ig G or cytoplasmic chains for these antibodies , but have a rearranged gene segment( meaning active ) for the T cell Receptor . So the Cells are T Cells

Third question : Now that we know that they are T Cells , we want to know whether they are CD4 or CD 8 positive

The cells in the clinical vignette lack both CD4 and CD 8 ( double negative ) According to how T cells normally develop - They start of as being double negative ( i.e not expressing CD4 or CD 8) in the subcapsular region and progressively become
- positive for both CD 4 and CD 8 in the cortex
- and eventually acquire the TCR and CD3 by the time they get to the medulla

These cells therefore must T lymphocyte thymocytes localised to the cortex

i_hate_it_here  FA2020 pg: 102 +
... cassdawg made a comment on nbme15/block2/q#30 (A 2-month old male infant with a ventricular septal...)
 +12 
submitted by cassdawg(931)

Here is my take: a ventricular septal defect in infancy allows for left to right shunting of blood in the ventricles. This causes an increased pressure in the right ventricle (due to more blood being pushed into it) and a decreased pressure in the left ventricle. Because there is more blood in the pulmonary circulation from the shunt, I think the left atrial pressure would also be increased in an early VSD.

SO when you repair the VSD, the left ventricle pressure will be increased compared to when the shunt was present (it is no longer losing blood), the right ventricle pressure will be decreased (it is no longer getting blood from the shunt), and the left atrial pressure will be decreased (there is no longer overload of the pulmonary system returning to the left atrium).

FA2020 p298

epiglotitties  ily cassdawg +3
i_hate_it_here  epiglotitties πŸ˜‚ +
... cassdawg made a comment on nbme15/block1/q#10 (When compared to oxygenated blood, deoxygenated blood carries more carbon dioxide for a given PCO2)
 +8 
submitted by cassdawg(931)

Deoxyhemoglobin has a higher pKa than oxyhemaglobin and thus will accept hydrogen ions more readily. This is important in the ability to "carry" CO2 as the main mechanism of CO2 transport is actually conversion of CO2 to HCO3- (CO2 + H2O -> HCO3- + H+), thus deoxyhemaglobin carries the H+ while HCO3- is transported in the plasma to the lungs. Carbaminohemaglobin is actually only about 20% of the CO2 trasnport and CO2 dissolved as CO2 is 10%; trasnport as HCO3- is around 70% of the CO2 transport.

Here is another image of the process.

Another important aspect of the process to take note of that they like to ask about is the chloride shift. Chloride moves the opposite direction as HCO3- in the RBC. Thus at tissues where we are generating HCO3- from CO2 and need to pump it out of the cell, chloride moves into the cell.At the alveoli where we need to pump HCO3- back into the RBC to turn it into CO2, chloride moves out of the cell.

Other answers:

  • 2,3BPG will bind and stabilizes deoxyhemaglobin making it less attracted to oxygen, shifting the hemaglobin dissosiation curve right.
  • Deoxyhemaglobin has a higher capacity to form carbanimohemaglobin
  • Deoxyhemaglobin has a higher pKA than oxyhemaglobin (this is why it can accept hydrogen ions more readily)
  • Competition for binding site is not a major mechanism for the ability to carry CO2 as most CO2 is "carried" by conversion to HCO3-
  • Nitric oxide binding is not a mechanism of CO2 carry.
pakimd  @cassdawg thank you for explaining so well along with explaining all the answer options. +
... andro made a comment on nbme15/block4/q#26 (65 yo woman, follow-up examination, DEXA scan shows decreased bone density)
 +8 
submitted by andro(170)

First step is to make the presumptive diagnosis of osteoporosis from the clinical vignette . ( The supposed subtype in our patient is postmenopausal osteoporosis)

After this the next step is to make an association with the lab findings The primary defect is a deficiency of estrogen . Normally estrogen decreases osteoclast activity by

  1. inducing apoptosis
  2. increased formation of osteoprotegerin a decoy molecule which inhibits activation of RANK receptors

Net effect of losing estrogen is increased osteoclast activity ,and in this question by extension RANK L concentration .

NOTE : ALP which is an indicator of osteoblast activity does not change/ increase in osteoporosis , as such avoid all options with an increase in osteoblast activity

brise  But wouldn't you need osteoblasts to have RANK L? +4
cassdawg  You still have osteoblasts, they just aren't doing their "build bone" job so their primary activity is decreased. Rather, they are stimulating osteoclasts by increasing RANKL. Similar to how parathyroid hormone stimulates osteoclasts through osteoblasts --> the osteoblasts are involved but not in doing their "build bone" job; however you would never say you increase osteoblast activity with PTH even though they are necessary for PTH function. +3
... andro made a comment on nbme15/block4/q#33 (During normal skeletal muscle twitching, ATP concentration does not fall significantly.)
 +7 
submitted by andro(170)

A note to self : Creatine phosphate is a short term energy source in muscle . Acts by donating phosphate groups to regenerate ATP .

*Creatine is derived from Arginine and metabolised to Creatinine ( which is excreted by the kidneys )

cheesetouch  ATP on FA2018 p74 to annotate book +1
... cassdawg made a comment on nbme15/block1/q#45 (A 70-year-old man has a 4-month history of weight...)
 +7 
submitted by cassdawg(931)

The description points to pancreatic insufficiency due to steatorrhea (fat in the stool, likely due to insufficiency of pancreatic lipase) and muscle fiber in the stool (which points to incomplete protein digestion, likely due to insufficiency of pancreatic proteases).

Further, he has no deficiency in carbohydrate absorption as evidenced by the D-xylose test (which indicates an intact mucosa for absorption and does not require digestive enzymes, FA2020 p373); and he has no abnormalities on biopsy of the intestine.

Thus, the primary issue is pancreatic insufficiency and supplementation of pancreatic enzymes is most helpful.

cheesetouch  FA2018 P375 +
... cassdawg made a comment on nbme15/block3/q#3 (A 3-year-old boy with chronic otitis media is...)
 +7 
submitted by cassdawg(931)

Important aspects of volatile (gas) anesthetics: (FA2020 p549):

  • MAC (minimum alveolar concentration): essentially the ED50 for inhaled anesthetics, this is the minimum concentration of anesthetic that causes a response in 50% of patients
  • LOW MAC means HIGH potency - more potent drugs would have a lower minimum amount needed to be present in the alveoli in order to exert their effect.
  • LOW MAC is related to HIGH lipid solubility (higher oil/gas partition coefficient) - more lipid soluble agents tend to be more potent because of their increased ability to cross the BBB
  • MACs are additive (i.e. one gas at 1.5 MAC = two gases at 0.75 their respective MACs)
  • Blood/gas partition coefficient: an expression of solubility; anesthetics with a low blood gas partition coefficient have a rapid onset/offset
  • i.e. LESS plasma solubule anesthetic = FASTER onset/offset
  • This is because less plasma soluble agents will "fill up" their maximum amount in the blood reservoir quicker and thus are pushed down their concentration gradient into the brain quicker; i.e. they quickly saturate the blood and will move on to affecting the brain quicker
  • MAC and blood/gas partition coefficient also tend to be inversely related -- higher MAC = lower blood/gas partition coefficient and vice versa; thus many of the more potent anesthetics have a longer time for onset/offset
cheesetouch  FA2018 P532 +1
randi  FA2019 p536 +
... cassdawg made a comment on nbme15/block4/q#22 (A 32-year-old man has a 3-month history of episodic...)
 +7 
submitted by cassdawg(931)

I definitely did not know this, but apparently smoking can worsen GERD due to tendency of nicotine to cause relaxation of the lower esophageal sphincter. Smoking is also linked to stomach ulcers due to interference with gastric mucosa and acid production. Just don't smoke kids. Don't do drugs. Stay in school forever like med students.

i_hate_it_here  don't tell me what to do +
trazobone  Don’t you just love it here +
... fruitkebabs made a comment on nbme15/block1/q#35 (30 yo woman, uncomplicated vaginal delivery, delivers placenta but continued heavy blood loss)
 +6 
submitted by fruitkebabs(19)

Uterine atony is the most common cause postpartum hemorrhage due to failure of the uterus to effectively contract and retract after delivery. It is treated with uterine massage and oxytocin.

... cassdawg made a comment on nbme15/block1/q#50 (25 yo man participates in study of muscle function)
 +6 
submitted by cassdawg(931)

Botulism toxin acts via proteases that cleave SNARE and prevent acetylcholine release at the neuromuscular junction (FA2020 p132). Thus, it does not directly affect the post-synatpric muscle cell. If you add external acetylcholine, you would still have a completely normal response. This eliminates all but two answers.

The end plate potential (EPP) would be affected by botulism toxin because the end plate potential is the change in voltage that occurs at the postsynaptic muscle motor endplate after an action potential in the motor neuron axon triggers release of many acetylcholine vesicles. Normally, an action potential in the motor neuron will cause influx of calcium that leads to fusion of Ach vesicles (requiring SNARE) and exocytosis, releasing large quantities of Ach into the synapse which can then bind and trigger an EPP in the muscle. With botulism, fusion of the Ach vesicles is inhibited so less Ach is released and the EPP is blunted. Notably, the voltage is the same as the mEPP which is the voltage after random occurrence of Ach release (see below).

A miniature end plate potential (mEPP) is the voltage change that occurs when one vesicle of acetylcholine is released. These occur randomly. mEPP would not be affected by botulism toxin because it is the produce of random fusion of a vesicle which could still occur after administration of botulism toxin.

Here is an image reminding the difference between EPP and mEPP.

... ergogenic22 made a comment on nbme15/block2/q#26 (47 yo man, admitted to hospital for myocardial infarction)
 +6 
submitted by ergogenic22(301)
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utcAe IM and almirt grugre rfom( eht )mruumr dlsea ot VL lferaui nad blckawfo of olobd iton het ugnsl.

hsTi edasl ot neicdesar myoulpanr tcohayitrds laycilarp esse.rrup Tshi illw lade to xecses loumev giakeln fomr the yulnroapm lacslipiare noti eht stlaettriini adn shti lliw metianfs sa apyormnul emdea rs(lc.)eack

nPoymraul amdee will nietfrree ithw gsa acehgenx aiedgln ot o.mexpaihy

medstudent  Doesn’t this also result in decreased alveolar ventilation since the fluid blocks air from getting to the alveoli? +3
cassdawg  ^I would agree, but I think the primary cause of hypoxemia in pulmonary edema is actually the diffusion defect rather than strictly the decrease in alveolar ventilation so the better (more NBME) answer would simply be the increased pulmonary capillary pressure as this is the root cause of all of the issues in this guy's oxygenation. +
cassdawg  Another way of saying this is that if the defect was purely due to a decrease in alveolar ventilation, the A-a gradient would be unchanged and CO2 would be increased. However, since it is edema, the A-a gradient is increased because there is a diffusion defect, and CO2 is not significantly increased. +1
... lola915 made a comment on nbme15/block0/q#0 (A 50-year-old man comes to the emergency department...)
 +6 
submitted by lola915(34)
  • Arterial: Pco2 30 mm Hg, Po2 96 mm Hg
  • Arterial O2 content: 12 vol% (N=17%–21%)
  • Mixed venous Po2 36 mm Hg
  • Mixed venous O2 content 8 vol% (N=10%–16%)

  • A) Anemia - Patient has nl PaO2 and decreased O2 content. Also patient is hyperventilating and CO2 is thus low.

  • B) Drug-induced alveolar hypoventilation - Arterial PO2 would be low&CO2 high
  • C) Residence at a high altitude - Arterial PO2 would be low
  • D) Severe regional mismatching of alveolar ventilation and pulmonary capillary perfusion - Pulmonary Embolus would cause a decrease in arterial PO2 E) Voluntary hyperventilation - Arterial O2% content would be nl

Anemia causes hypoxia without hypoxemia. Meaning low O2 delivery to tissues but not low O2 saturation of the blood. The lungs can adequately deliver O2 to the arterials so PaO2 is normal. Anemia causes low O2 content because you have relatively low amounts of Hb to carry oxygen.

O2 content = (1.34 Γ— Hb Γ— Sao2) + (0.003 Γ— Pao2)

... cassdawg made a comment on nbme15/block1/q#21 (A 20-year-old woman comes to the physician because...)
 +6 
submitted by cassdawg(931)

FA2020 p 612 has early fetal development. Here are the explanations for the answers:

Basically, even without knowing all the exact days of development, most answers can be eliminated based on having the events in the incorrect order or having an incorrect aspect about development (i.e. the syncytiotrophoblast forms concurrent with the cytotrophobast, 3 germ layers are present after gastrulation, the embryo is never truly resistant to teratogens after implantation, the sclerotome forms from somites so somites have to come first).

Here is a general overview of the first three weeks of development after fertilization.

Here is another one if that doesn't do it for ya.

cheesetouch  FA18 p 594, 599 (syncytiotrophoblast) +
... cassdawg made a comment on nbme15/block1/q#31 (A 75-year-old woman comes to the physician because...)
 +6 
submitted by cassdawg(931)

Lentigo maligna is a type of melanoma (FA2020 p484), hence why it is important the lesion is brown/black with irregular borders and enlarging (all hallmarks of melanoma). The biopsy description also fits lentigo maligna, but even if you are not a pathologist the description that fits cancer and and "atypical melanocytes" should point you to lentigo maligna.

  • Acanthosis nigricans is thickening (acanthosis means epidermal hyperplasia) and darkening of skin in folds and creases associated with insulin resistance
  • Actinic keratosis is a premalignant lesion that is a small, rough, erethematous or brownish papule/plaque
  • Compound nevus is a type of mole that is slightly elevated, brown or light brown, and has regular borders. It is not fast-growing.
  • Sebhorreic keratosis are "stuck-on" flat, greasy, pigmented squamous epithelial proliferation of immature keratinocytes with keratin-filled cysts. Rapid onset of multiple indicates possible GI malignancy.

FA2020 p482, 477 and 484

cheesetouch  fa2018 p 469 melanoma +1
randi  FA2019 p473 +
... specialist_jello made a comment on nbme15/block1/q#33 (75 yo woman, 1 day fever and back pain)
 +5 
submitted by specialist_jello(10)

NFKB is in its inactive state bound to IKB. As a part of the classical pathway, bacterial antigens bind to TLR and activate IKB kinase, (kinase phosphorylates)

  • IKB is ubiquinated and degraded

  • NFKB enters nucleus and synthesises the inflammatory stuff

Uw QID: 11955

... ergogenic22 made a comment on nbme15/block2/q#9 (67 yo man, 2 days double vision and drooping left eyelid)
 +5 
submitted by ergogenic22(301)
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He has a wond and tuo up,ipl dcsaeu yb NC III lsap.y isH gaez is due to npedooups icntoa of eth lreaalt crutse nda ourerpsi uob;lqie osipst ude to edtinoernva of vatleor ppblaeera sie.osusipr

eTh onyl yjurin tleisd taht ulcod cusae a CN III slypa si msenuyar fo the APC ignmscpreos eth oltrcuaroom .uecnusl

cheesetouch  Compression of superior cervical ganglion -> Horner's syndrome -> ptosis, miosis, anhidrosis, would NOT have dilated pupil. +1
jmd2020  Aneurysm of the PCA would compress the oculomotor NERVE, not the nucleus (just fyi) +1
trazobone  I appreciate u cheesetouch +
... cassdawg made a comment on nbme15/block3/q#10 (5 yo boy stung on foot by bee)
 +5 
submitted by cassdawg(931)

The primary mechanism of inflammation "tumor" or swelling is increased permeability of the endothelium which leads to leakage of fluids (FA2020 p213)

... cassdawg made a comment on nbme15/block3/q#24 (28 yo African American man, 3 months mild fatigue, weakness, 4.5 kg weight loss)
 +5 
submitted by cassdawg(931)

I don't like this question for many reasons, but basically he has sarcoidosis (noncaseating granulomas with no pathogen found on biopsy) which according to First Aid is more common in African-American females. Since he is African-American that is his risk factor (FA2020 p676).

cheesetouch  FA2018 p658 +
i_hate_it_here  Questions like this let me know that the ideals of racism have never left the medical system. Ok, so he's "African-American", is he of actual African descent? Is sarcoidosis just increased in american found black people, or is it black people of African descent, what about Jamaican? Afro-Latino, Europeans?? I hate that they teach us things like this and we're suppose to take it at face value. +1
kaf  agree...medicine is full of racism, sexism and so on. Some meds work differently and diseases present differently etc...for ex., ACE inhibs in AA vs white...or MI presentation in women vs men. +
... cassdawg made a comment on nbme15/block3/q#48 (A study finds a statistically significant difference between two groups when, in reality, there isn't one. What is the name of this statistical error?)
 +5 
submitted by cassdawg(931)

In hypothesis testing, the alpha value is the probability of making a Type I error. This is the type of error mentioned in the question.

  • Type I error - you find a difference when a difference doens't really exist.
    • One way of remembering this is that this is what scientists "want" to make: they want to find a significant difference in their data, thus it is the "first mistake" they'd make.
    • Alpha is the probability you are willing to accept that you could have made a type I error (i.e. an alpha value of 0.05 means there is a 5% probability you could make a type I error and reject the null hypothesis when you should not)

  • Type II error - you do not find a difference when you should have because a true difference really exists
    • Beta is the probability that you make a type II error
    • Power is equal to (1 - beta)
    • Power can be increased by increasing sample size, and thus with a larger sample you have a lower probability of making a Type II error
    • Power can also be increased by increasing expected effect size or increasing precision. It is interesting to note accuracy has no effect on power.

FA2020 p263

cheesetouch  FA2018 p258 +
... baja_blast made a comment on nbme15/block4/q#48 (Study of effectiveness of cough medication in children)
 +5 
submitted by baja_blast(91)

In this study, a placebo is not used on the control group. The experimental group gets dextromethorphan while the control group gets "no treatment". This results in procedure bias, as subjects in different groups are not treated the same. Blinding and use of a placebo reduce the influence of participants and researchers on procedures and interpretation of outcomes as neither are aware of group assignments.

See table on bias and study errors in FA 2019 p 260.

... cassdawg made a comment on nbme15/block1/q#13 (A 24-year-old man develops recurrent vesicular...)
 +5 
submitted by cassdawg(931)

This is likely Herpes Simplex Virus 1 (based on the vesicular lesions on the lip) which remains dormant in sensory ganglia, most commonly the trigeminal ganglion (FA2020 p164).

... cassdawg made a comment on nbme15/block2/q#24 (An 82-year-old woman with alcohol dependence is...)
 +5 
submitted by cassdawg(931)

This woman has the classic signs of vitamin C deficiency, or scurvy: easy bruising, petichiae, perifollicular hemorrhages, gum disease, and slow wound healing. Vitamin C is necessary for proper hydroxylation of proline and lysine in collagen. (FA2020 p69 [nice])

... cassdawg made a comment on nbme15/block3/q#41 (A 56-year-old woman is brought to the emergency...)
 +5 
submitted by cassdawg(931)

Here, we want to know loading dose which is equal to the volume of distribution x target concentration in plasma.

So our loading dose = 1.81L/kg x 10mg = 18.1mg/kg

She is a 55kg person so 18.1mg/kg x 55kg = 995.5 mg which approximates to 1000mg total loading dose.

Important Pharm Equations to Remember

cassdawg  10mg/L * sorry +
cheesetouch  fa2018 p229 +
... cassdawg made a comment on nbme15/block1/q#11 (9 yo boy, mild mental retardation, 4 years increasingly frequent major motor seizures)
 +4 
submitted by cassdawg(931)

Tuberous sclerosis is characterized by HAMARTOMASS [Hamartomas in CNS and skin, Angiofibromas , Mitral regurgitation, Ash-leaf spots , cardiac Rhabdomyoma, (Tuberous sclerosis), autosomal dOminant; Mental retardation (intellectual disability), renal Angiomyolipoma , Seizures, Shagreen patches, FA2020 p525]

If you didn't know what hamartomas look like (i.e. me), here is a picture of what they were describing. They also describe seizures, subependymal calcified nodules (likely hamartomas of the CNS), and a cardiac mass, which is likely a rhabdomyoma. These are characteristic of Tuberous Sclerosis.

Wrong answer explanations:

  • Familial hypertrophic cardiomyopathy is associated with sudden death in athletes, not seizures and hamartomas.
  • Gardner Syndrome is also called familial colorectal polyposis and is a form of familial adenomatous polyposis.
  • Glycogen storage disease Type I is Von Gierke disease, which presents with hepatosplenomegaly and severe fasting hypoglycemia typically in infancy.
  • Multiple Endocrine Neoplasia Type I is associated with all the P's -> Pancreatic, Parathyroid, and Pituitary (pancreatic endocrine tumors, parathyroid adenomas, and pituitary tumors)
... andro made a comment on nbme15/block1/q#24 (3 yo girl, 2 weeks of diarrhea)
 +4 
submitted by andro(170)

Note: IL-12 receptor deficiency, or a defect in the Interferon Gamma receptor
Think Disseminated Mycobacterial and Fungal Infections . Also salmonella *

cassdawg  Disseminated mycobacterial infections occur more often with interferon gamma receptor or IL-12 receptor deficiencies due to impaired ability to form granulomas (IL-12 and IFNgamma are the main cytokines involved in granuloma formation). +2
cheesetouch  FA2018 P 116 under il-12 receptor deficiency +1
cheesetouch  Also on FA18 p 102 related to Th1 response +
... ergogenic22 made a comment on nbme15/block2/q#28 (35 yo woman, gravida 1, para 1, 2 months generalized weakness and fatigability)
 +4 
submitted by ergogenic22(301)
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asiccls yshametain sairvg per.cuti nssWeor wthi s.ue xS eudilnc ioa.plpdi mpeIemnrvto twhi E.hCA

soAl isde ,tneo tno'd suocf on the gncanrepy ustat,s tbu emwon woh rae ni the amusprttop oerid are ta alpruircltay hhig srik fo epnogevild easnhiatym vgsiar

pakimd  why are answers unscrambled on here? +
... ergogenic22 made a comment on nbme15/block2/q#43 (37 yo woman, brought to ER by husband after being found unconscious)
 +4 
submitted by ergogenic22(301)
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lCoo and plae ireextmtsie lsuer uto itrteiivudbs ecassu ,nce(ouiegnr n,aihxapysla ic)s.tep

ciHmlovopye doulw becirdse a cosreps of uvmloe loss e(beginld or eyon)iatdrhd dan oludw tno lnexaip teh lkcsarec or guajlur neiv isnnidos.et

dnt'o be hnotwr off yb het lrmnoa herat nu.ssod

baja_blast  Raise your hand if you were also thrown off by the normal heart sounds. +6
jmd2020  I think this question is poorly constructed. Cardiogenic shock would result in an INCREASE in SVR - this woman's BP is 70/40... +1
drdoom  @jmd2020 low BP does not mean the SVR isn't increased β€” it /is/ increased! it's just that the heart is so effed up that even massively increased SVR is not enough to maintain good pressure +2
drdoom  another way to explain: imagine you are losing blood volume at a constant rate (someone punched a tube into your aorta and draining you like a pig); at first, your heart would beat stronger (ionotropy) and faster (chronotropy) to maintain BP; at the same time, all your arterioles would constrict to maintain blood flow rates (and perfusion) to vital tissues ... but at some point you will have lost so much blood that all the ionotropy, chronotropy & SVR in the world could not save you or your BP .. your BP will plummet no matter what compensatory mechanisms your body has up its sleeve. +2
... cassdawg made a comment on nbme15/block3/q#3 (56 yo woman, brought to ER, 2 hours fever and shortness of breath)
 +4 
submitted by cassdawg(931)

Lipopolysaccharide, or LPS, is the primary endotoxin mediator of gram(-) sepsis leading to septic shock. This woman likely has sepsis from E. coli, a gram negative bacterium which produces LPS, based on her history indicating a UTI. E.coli are the most common cause of UTI. (FA2020 p133)

cheesetouch  FA2018 p145 +3
... cassdawg made a comment on nbme15/block3/q#18 (27 yo man, 3 hours nausea, cramping abdominal pain, diarrhea)
 +4 
submitted by cassdawg(931)

FA2020 p144

An USMLE testable fact about salmonella species is that antibiotic use actually prolongs the excretion of the organism. Fun fact(?) for memorization as there is no clear answer as to why that I could find.

hiroshimi  Have a card in Zanki saying this using abx with salmonella can cause HUS so may be it's linked? +
... cassdawg made a comment on nbme15/block4/q#38 (25 yo woman, 1 week general malaise, facial rash)
 +4 
submitted by cassdawg(931)

Based on the question stem and the autoanitbodies given (butterfly rash combined with anti-dsDNA/anti-Sm/antiphospholipid), this woman has classic lupus. SLE is associated with cytopenias, so thrombocytopenia is the best choice of the available answers. Thrombocytopenia is common in lupus (FA2020 p470)

  • HUS is associated with E.coli or Shigella infection and not Lupus. Lupus kidney disease is diffuse proliferative glomerulonephritis.
  • Macrocytic anemia is typically caused by B12 or folate deficiency and not associated with lupus. Lupus anemia is typically anemia of chronic disease, which is normocytic, or due to inadequate RBC production or iron deficiency, which is microcytic.
  • Multiple nucleated erythrocytes are found in leukemias when the RBCs are being "pushed" out of the bone marrow, or in diseases where the bone marrow is highly stressed. Lupus does not typically cause this.
  • I am not 100% sure why rouleax formation is wrong, because as far as I understand any condition that increases monoclonal Abs can cause rouleaux formation, but I am assuming it is just not as common/likely, hence thrombocytopenia which is very common is the better answer
cheesetouch  FA2018 P458 +1
randi  FA2019 p462 +
... cassdawg made a comment on nbme15/block4/q#5 (A 6-year-old girl is brought to the physician for a...)
 +4 
submitted by cassdawg(931)

TL;DR: Even with Type I or II renal tubular acidosis the ammoniagenesis from glutamine is not impaired and thus is the main source of ammonia.

Here is my take: Based on her history and measured plasma values, this girl likely has one of the "low potassium" renal tubular acidoses, either Type I or Type II (see this chart for reasoning based on measured values or this image for fun colorful renal tubular acidosis and FA2020 p593)

Then, we are told that she has a defect in "ammoniagenesis". In the renal tubules, ammonia is generated in two primary ways: via direct conversion of glutamine to ammonia in the proximal tubule which is then secreted into the tubule, or by NH3 combining with with H+ in the collecting tubules (which I guess they are considering a separate ammoniagenesis pathway even though its all kinda related?). See this diagram or this diagram

Assuming our girl has Type I renal tubular acidosis, there will be decreased availability of hydrogen ions in the renal tubules to combine with NH3. Thus, the primary source of ammonia production in this patient will be glutamine (which is the major source of ammoniagenesis in a normal person anyways).

Further reasoning - Type I is impaired secretion of hydrogen ions into the lumen, so there will be less hydrogen ions available. She likely has type I because this is primarily treated with potassium citrate (both to buffer and to prevent renal stones which are a common complication). Even if she had Type II the increased excretion of bicarb would also buffer more H+ leaving less for ammoniagenesis in the NH3/H+ combination fashion.

Contrarily, Type 4 renal tubular acidosis (hyperkalemic) results in decreased synthesis of ammonia in the proximal tubules, which we know she does not have because of her low potassium.

cheesetouch  Cassie you're a god. Simple/stupid approach to make a good guess - if she cannot make ammonia in the kidney, main ammonia source probably from an exogenous form like amino acids -> Glutamine! +2
pakimd  thank you @cassdawg, you're amazing! +
... cassdawg made a comment on nbme15/block3/q#6 (A 45-year-old man has a 2-day history of severe...)
 +4 
submitted by cassdawg(931)

Based on the history (consumption of large amounts of alcohol and elevated serum amylase/lipase with hypocalcemia), this man likely has acute pancreatitis (FA2020 p397). One of the major complications is autodigestion of tissues, such as what is seen in the image.

cheesetouch  FA2018 P391 +
epiglotitties  Can anyone explain/describe the image? I got it right based on the info from the question but would like to know anyways just for future reference +
randi  FA2019 391 It's also not alcoholic hepatitis because this "requires sustained, long term consumption" of alcohol and this patient consumption over the last few days. FA2019 395 +
... cassdawg made a comment on nbme15/block3/q#23 (An investigator who wishes to test the hypothesis...)
 +4 
submitted by cassdawg(931)

Immunohistochemistry uses fluorescently tagged antibodies to bind specific antigens on tissues. In this case, an antibody could be directed against CD44v10 variant protein used to tag the cells in the samples that express the variant. This is also useful because it can be done on slides of paraffin embedded tissue.

  • Affinity column chromatography is used to separate a biochemical mixture based on interaction between antigen/antibody, enzyme/substrate, receptor/ligand, etc. but would not be useful in pre-embedded tissues or this case
  • Density gradient centrifugation is used on mixtures to separate them into components and is particularly useful in separating cell suspensions, such as in separating blood into layers to get the buffy coat with WBCs
  • Northern blot is for RNA and fluorescently tags a piece of RNA present in a sample
  • PCR is for identifying/anplifying a DNA segment
  • Reverse transcriptase (RT) PCR is typically used to measure expression levels of an mRNA
  • Southern blot is for identifying a DNA segment in a digest
... cassdawg made a comment on nbme15/block3/q#25 (A 67-year-old man comes to the physician because of...)
 +4 
submitted by cassdawg(931)

This man likely has diabetic neuropathy and thus would have neuropathic pain. Neuropathic pain is described as a burning pain as compared to the other kinds of pain.

Here are some differences between nocioceptive and neuropathic pain.

Here is a chart of descriptors used for neuropathic v nocioceptive pain.

trazobone  I appreciate u cassdawg +
... cassdawg made a comment on nbme15/block4/q#25 (A 25-year-old primigravid woman at 12 weeks'...)
 +4 
submitted by cassdawg(931)

This is a partial mole because of the presence of fetal parts. Complete moles have no fetal parts, partial moles have fetal parts(PARTial = fetal PARTs). (FA2020 p642)

cheesetouch  FA18 p 622 +
... fruitkebabs made a comment on nbme15/block1/q#6 (7 yo boy, 1 day fever, headache, nonproductive cough)
 +3 
submitted by fruitkebabs(19)

Oseltamivir and zanamivir are influenza neuraminidase inhibitors. Typically, neuraminidase allows influenza particles to bud off host cells. Without the functioning enzyme, the virion buds cannot detach from the host cell membrane.

cheesetouch  FA2018 P201 +
... andro made a comment on nbme15/block1/q#39 (Investigator study, new behavioral program for attention-deficit/hyperactivity disorder (ADHD))
 +3 
submitted by andro(170)

The uneven distribution of ADHD based on gender(more cases of ADHD among boys ) is a potential confounder , and so STRATIFICATION addresses this

pakimd  how is a disease more common in one age group a confounder? +
... fruitkebabs made a comment on nbme15/block1/q#50 (25 yo man participates in study of muscle function)
 +3 
submitted by fruitkebabs(19)

Although botulism blocks ACh release, it wouldn't have effects on mpp and the response to exogenous ACh provided to the synaptic junction. The potentials would be the same as it would normally be. The epp difference was disclaimed in the question stem.

djeffs1  @cvan, thats what I was thinking. This question was worded weird and i'm still trying to figure out how it was referring to testing in a different setup than the one discussed in the stem... +
... cassdawg made a comment on nbme15/block2/q#11 (48 yo man, brought to ER, 1 hour nausea, crushing chest pain)
 +3 
submitted by cassdawg(931)

This woman's cardiac arrest caused a period of loss of blood flow and ischemia in the kidney that has led to acute tubular necrosis. In ATN there is an inciting event then an oliguric phase. In ATN, there is death of renal tubular epithelial cells that slough off and form muddy brown granular casts. Keep in mind the proximal tubule and thick ascending limb are the part of the kidney most susceptible to hypoxic injury. [FA2020 p602]

... ergogenic22 made a comment on nbme15/block2/q#15 (64 yo man, 2 months progressive shortness of breath)
 +3 
submitted by ergogenic22(301)
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CLT eedacdres tsseugsg civeitrrtse ds.eeasi recluatRi naptert sggsuets nprmayuol rfibssio

cheesetouch  fa2018 p657 +
whk123  So after seeing clubbing of fingers we have two D/D's in our mind 1)Bronchiectasis (a type of COPD in which TLC increases your lungs expand due to obstruction air can't go out from lungs so air keeps on expanding lungs) 2)Idiopathic pulmonary fibrosis why IPF is a ans here because in q stem TLC is decreased and the coarse reticular pattern (honeycomb appearance) is also a giveaway. +
... ergogenic22 made a comment on nbme15/block2/q#36 (72 yo woman, admitted to hospital for acute myocardial infarction)
 +3 
submitted by ergogenic22(301)
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Tihs niuoteqs is aikngs htwa ltfe tnnaimod cticonrlaiu asme.n I sseppuo ti snwta su to rnfie tath het DPA is nsyiugplp hte hmapdagir rscfeua and VA dnoe.

It si gfnocsnui to em basuece mollnray eth tihRg naarmlig taeyrr ppsuelsi hte aamphgtadiicr dborre c(ueta )amrgni of the ea.rht Im' not sure hatt ti shcaegn in tlef indnmtoa cutronila.ic terruhmreoF it duowl nto cbrnha off hte DAP, huhaoltg yebam tpras fo it aer eispudpl by teh PAD

sAol eht AV endo si uspepdil by het renraitvAtucoirl dnola ,rratye chiwh nac be a bhnacr fof of teh CAL ro het XCtLub ont lraeyl hte PAD

v3b7ir:.s/tgham//ponhicw.mpMt/915ePswwlctn.in/c/3C9l.

os ngifcunso qniutsoe orf em utb hte ntopi is to ownk teh uoscre fo ltfe nmoatnid oinrlcuicta to teh ADP

epiglotitties  What the heck is it with this scrambling?😑 +
5thgencephalosporin  you need to be a member to have total access to the content +
... ergogenic22 made a comment on nbme15/block2/q#40 (4 yo boy, 2 months progressive weakness, loss of muscle function)
 +3 
submitted by ergogenic22(301)
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sCcalis icrpuet orf enueDnhc lcumasru ptdyy.orsh wcihh si due ot ldeetde storiynhpd ent.ipro

Frmo AF: psDn"yrioht hlspe hcnrao cemusl ,firsbe ralyipirm in eakleslt dan idarcca .mlsuce It cecnsnto teh aualilnrelrtc ynctosoeetlk acit(n) ot teh ansmreratnebm osnitrep Ξ±- adn -olΞ²astrcy,gdyn hiwch aer nnoedtecc ot eth auetrrxcllela matixr E(")CM

cheesetouch  fa2018 p61 +1
... ergogenic22 made a comment on nbme15/block3/q#6 (50 yo man, routine health maintenance examination)
 +3 
submitted by ergogenic22(301)
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rlMulayed hdoyirt nciaoamrc is iddefne a:s

a laninatmg nrlftoiopraei fo lulrflcariopaa "C" elcsl that rscetee ntlaciinco

sotgyohli shsow maaltnnig turom lecls wihnit nipk i)na,lyh( madiyol roamst

... cassdawg made a comment on nbme15/block3/q#47 (2-month-old boy, hypotonia and poor feeding since birth)
 +3 
submitted by cassdawg(931)

Peroxisomes are where degradation of very long chain fatty acids occurs (as well as phytanic which is a branched chain fatty acid and pipecolic which is an alpha amino acid) [FA2020 p47]

... cassdawg made a comment on nbme15/block4/q#5 (Male newborn delivered at term with right-sided aortic arch)
 +3 
submitted by cassdawg(931)

This indicidual has CATCH22 DiGeorge Syndrome, caused by failure in the development of the 3rd and 4th pharyngeal pouches (FA2020 p116). This is evidenced by the hypocalcemia (agenesis of parathyroids), facial deformities, and conotruncal abnormality (right sided aortic arch).

Big thing is being able to ensure you know it is pharyngeal POUCH not cleft or arch. Pharyngeal arch derivatives are on FA2020 p620. Pharyngeal pouch derivatives are p621. And pharyngeal cleft derivatives are p619. (Aortic arch derivatives are p619 as well, if you want to complete the circle)

Treacher-Collins is error in 1st and 2nd pharyngeal arch derivatives which can present with craniofacial abnormalities, zygomatic and mandibular hypoplasia, and hearing loss. Pierre Robin is similar and presents with micrognathia, glossoptosis, cleft palate, and airway obstruction. Neither of these would present with hypocalcemia.

cheesetouch  FA2018 P602-603 arches/pouches +
cheesetouch  Arch vs pouch (my thoughts): Arches help build a structure and direct development of cartilage, muscles, nerves. Pouches are cavities or minor organs (middle ear cavity, eustachian tube, thymus, parathyroids). +5
... cassdawg made a comment on nbme15/block4/q#40 (18-month-old boy, severe combined immunodeficiency syndrome)
 +3 
submitted by cassdawg(931)

From what I can tell, the gist of this question is that he has SCID and since the SCID child has basically no immune system (particularly because the lack of T-cell immunity) there is a higher chance of transfusion-associated graft versus host disease (TA-GVHD) so blood products have to be irradiated.

Here is a medscape reference with who requires irradiated RBCs due to increased risk of TA-GVHD for your perusing.

i_hate_it_here  Just curious, are you a student? Your answers are always much appreciated. +2
... hungrybox made a comment on nbme15/block0/q#0 (An investigator is studying Helicobacter pylori...)
 +3 
submitted by hungrybox(968)

Excess pattern repeats lead to strand slippage/errors due to an unstable region (in this case, excess Cytidine bases).

It could be a repeated pattern as well (ie the trinucleotide repeat CAG in Huntington's).


here's a more in depth explanation (from wikipedia article on Slipped-strand mispairing):

A slippage event normally occurs when a sequence of repetitive nucleotides (tandem repeats) are found at the site of replication. Tandem repeats are unstable regions of the genome where frequent insertions and deletions of nucleotides can take place, resulting in genome rearrangements.

hungrybox  Anyone know why it's not Transposon insertion? I was thinking maybe because transposons have to be longer than one nucleotide, but I'm not sure. +3
bingcentipede  @hungrybox I think it's because transposons are usually gene segments rather than a single nucleotide insertion - plus w/ what you said about the repeated pattern, I think slipped-strand mispairing (which is a concept the NBME loves) more likely. +19
i_hate_it_here  cool so why do I need to know this +
... hungrybox made a comment on nbme15/block0/q#0 (A 22-year-old man comes to the physician because of...)
 +3 
submitted by hungrybox(968)

(wrong answer explanation)

Intermittent obstruction of the common bile duct is wrong.

Biliary tract obstruction would have:

↑↑ direct (conjugated) bilirubin (normal 0.0-0.3, pt was 0.4)

↑ Alkaline phosphatase (normal = 20-70, pt was 35)

hungrybox  source: pathoma +
... cassdawg made a comment on nbme15/block0/q#0 (A 1-month old male newborn is brought to the...)
 +3 
submitted by cassdawg(931)

This is a case of albinism, most likely due to decreased tyrosinase activity or decreased tyrosine transport (both are required in synthesis of melanin). Thus, there is a normal number of melanocytes and a decreased amount of melanin.

Vitilligo (characterized by irregular hypopigmented patches) is caused by destruction of melanocytes and thus would have decreased melanocytes.

FA2020 p476

... jackie_chan made a comment on nbme15/block1/q#22 (A 30-year-old nulligravid woman comes to the...)
 +3 
submitted by jackie_chan(16)

Hey Peter

Go sincerely fuck yourself with a 10 foot pole.

Love

Med students

jackie_chan  50$ a month when all content is contributed by the community, wheres my cut? +2
jackie_chan  Wheres every contributor's cut? +3