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(nbme24#21)

Can someone explain this one––I didn't really know what to make of the lab values. Clearly she was taking too much insulin, but how can you differentiate factitious disorder from a type 1 diabetic who takes too much of their insulin dose?

m-ice  I think the trick here is that they don't mention that the daughter has a history of Type 1 DM, so she has no reason to be taking insulin at all. She's definitely receiving insulin, but we don't have any history implying she's a type 1 diabetic. That, combined with the fact that there have been multiple episodes like this one, favors that the mother is giving the daughter insulin when she doesn't need it.
sajaqua1  C-peptide is produce by endogenous insulin, but is not part of exogenous insulin. She has elevated insulin, with low C-peptide, so she is receiving too much exogenous insulin. A history of recurrent episodes this year implies a behavioral issue; Factitious disorder imposed on another (also called Munchausen syndrome by proxy).

submitted by wired-in(46),

Maintenance dose formula is (CssCltau)/F where Css is steady-state target plasma conc. of drug, Cl is clearance, tau is dosage interval & F is bioavailability.

Neither dosage interval nor bioavailability is given, so ignoring those & plugging in the numbers (careful to convert units to mg/kg/day): (12 ug/mL * 1 mg/1000 ug) * (0.09 L/hr/kg * 1000 mL/1 L * 24 hr/1 day) = 25.92 mg/kg/day

...which isn't any of the answer choices listed. They must have rounded 0.09 L/hr/kg to 0.1 L/hr/kg, and doing so gives exactly 28.8 mg/kg/day (choice C)

lispectedwumbologist  That's so infuriating I stared at this question for 20 minutes thinking I did something wrong +35
hyoid  ^^^^^ +5
seagull  lol..my math never worked either. I also just chose the closest number. also, screw this question author for doing that. +4
ht3  this is why you never waste 7 minutes on a question.... because of shit like this +7
yotsubato  Why the FUCK did they not just give us a clearance of 0.1 if they're going to fuckin round it anyways... +10
bigjimbo  JOKES +
cr  in ur maths, why did u put 24h/1day and not 1day/24h? if the given Cl was 0.09L/hr/kg. I know it just is a math question, but i´d appreciate if someone could explain it. +
d_holles  LMAO games NBME plays +1
hyperfukus  magic math!!!!! how TF r we supposed to know when they round and when they don't like wtf im so pissed someone please tell me step isn't like this...with such precise decimal answers and a calculator fxn you would assume they wanted an actual answer! +1
jean_young2019  OMG, I've got the 25.92 mg/kg/day, which isn't any of the answer choices listed. So I chose the D 51.8, because 51.8 is double of 25.9......I thought I must have make a mistake during the calculation ...... +2
atbangura  They purposely did that so if you made a mistake with your conversion like I did, you might end up with 2.5 which was one of the answer choices. SMH +1
titanesxvi  I did well, but I thought that my mistake was something to do with the conversion and end up choosing 2.5 because it is similar to 25.92 +1
makinallkindzofgainz  The fact that we pay these people 60 dollars a pop for poorly formatted and written exams boggles my mind, and yet here I am, about to buy Form 24 +2
qball  Me after plugging in the right numbers and not rounding down : https://i.kym-cdn.com/entries/icons/original/000/028/539/DyqSKoaX4AATc2G.jpg +1

submitted by medstruggle(10),

Why is it aphthous ulcers if there are no GI symptoms? Why can’t it be herpes zoster?

colonelred_  It’s just canker sores, they come and go. I think in herpes the gingivostomatitis really only happens when you first get infected. After that you just get recurrent cold sores. +1
hyoid  Herpes zoster is not the same as herpes simplex virus. +11
bigjimbo  you would see dermatome rash in zoster +1
kateinwonderland  cf) Just in case someone wanted to know the causative organism of aphthous ulcers :The precise cause of canker sores remains unclear, though researchers suspect that a combination of factors contributes to outbreaks, even in the same person. Unlike cold sores, canker sores are not associated with herpes virus infections. +3
charcot_bouchard  Herpes Zoster doesnt cause gingivostomatitis. Herpengina can cause vesicular lesion in mouth but happens to children in summer season by entero virus +
drdeeznuts1  I'm wondering if this could be a mild case of Behcet syndrome without genital involvement +
sherry  It sure can be Behcet or Pemphigus if the q provides us with more info. Canker sores just come and go for years with unclear mechanism. Also herpes zoster is shingles by VZV, not HSV1. +

submitted by welpdedelp(137),

Ok, so RNA dependent DNA polymerase is for reverse transcriptase... single stranded + use RNA dependent RNA polymerase. Can someone explain?

hyoid  The only thing I can think of is that HIV is a (+)-sense single-stranded RNA virus that relies on an RNA dependent DNA polymerase (reverse transcriptase) to synthesize DNA. +
haliburton  according to [medbullets link](https://step1.medbullets.com/step1-microbiology/104196/rna-viruses_) ns ss RNA must carry RNA dependent RNA polymerase (so that is out). also, according to medbullets there are very few ds RNA viruses, so "most likely" will be ss. Also, RNA-dependent DNA polymerase = Reverse Transcriptase. Since HIV is a ss ps RNA virus with RT, they've described an HIV cousin. not sure beyond this. +
some0217710  Can’t think of any retroviruses outside of HIV and HTLV and they’re both +ssRNA +1