NBME 24 Factitious disorder imposed on another (NBME Answers)

Retired NBME 24 Answers

nbme24/Block 3/Question#21 (reveal difficulty score)
A 7-year-old girl is brought to the emergency ...
Factitious disorder imposed on another 🔍 / 📺 / 🌳 / 📖
tags: psych

+4 upvote downvote
submitted by ∗jkan(28)

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c-peptide is low with exogenous insulin. (c-peptide made as a byproduct of insulin production in the body) repeated visits+ high insulin+low c-peptide= exogenous insulin abuse. In a child-> factitious by proxy

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sunshinesweetheart ugh, I feel like a child could misuse their insulin by accident without proper supervision. Totally thought she had T1DM and not enough guidance on how to use the meds. annoying +3

peqmd I couldn't rule out if the child was trying to get swole and had a shady dealer. +3

alwaysdivs94 Sorry, where doesn't it talk about insulin abuse in the question? I thought she was administered for an acute exacerbation of heart failure? +

jaramaiha The issue was that the kid had 3 previous ED visits for similar symptoms in the past year. You'd think they would understand how their insulin works by then, so someone (her mom) is causing her to take too much insulin. +

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submitted by ∗groovygrinch(39)

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For those who were wondering like me, they gave the Beta-hydroxybutyrate (a ketone body) levels in order to rule out DKA (diabetic ketoacidosis) in a type 1 diabetics and which would otherwise not be distinguishable based only on C-peptide and insulin levels

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therealslimshady Regardless of the ketones, DKA is not likely anyway, since you'd see hyperglycemia in it, but this patient has hypoglycemia +

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submitted by ∗hyoid(46)

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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?

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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. +21

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). +8

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