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
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).
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.
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.
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
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
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 )
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.
Important aspects of volatile (gas) anesthetics: (FA2020 p549):
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.
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.
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.
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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.
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 × Hb × Sao2) + (0.003 × Pao2)
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).
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.
FA2020 p482, 477 and 484
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
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The primary mechanism of inflammation "tumor" or swelling is increased permeability of the endothelium which leads to leakage of fluids (FA2020 p213)
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).
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.
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.
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).
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])
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.
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:
Note: IL-12 receptor deficiency, or a defect in the Interferon Gamma receptor
Think Disseminated Mycobacterial and Fungal Infections . Also salmonella *
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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)
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.
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)
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.
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.
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.
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.
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)
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.
The uneven distribution of ADHD based on gender(more cases of ADHD among boys ) is a potential confounder , and so STRATIFICATION addresses this
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.
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]
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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]
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.
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.
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.
(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)
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.
Go sincerely fuck yourself with a 10 foot pole.