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NBME 22 Answers

nbme22/Block 2/Question#50

An 18-month-old boy is admitted to the hospital ...

Tuberous sclerosis complex

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submitted by armymed88(13),

Hypopigmented lesions refer to Ash-leaf spots, CNS lesions likely hamartomas . TS also associated with seizures.

fcambridge  How is Tuberous Sclerosis the most likely given that it is an AD disorder and there is no family history of "seizure disorder or major medical illnesses"? +1  
d_holles  @fcambridge variable expressivity of TSC allows for many different phenotypes. +  




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submitted by bubbles(27),

Can someone could explain to me how this is unequivocally tuberous sclerosis despite NF-1 and Sturge-Weber also presenting with skin lesions, hypopigmented macules, and seizures?

And considering the negative family history, I would have assumed that a sporadic mutation (like SW) would be more likely...

cocoxaurus  This question was tricky! Tuberous sclerosis= Hypopigmented= Ash leaf spot (The skin lesion in NF is Hyperpigmented- Cafe au lait and in Sturge Weber it's a port wine stain (also not hypopigmented). I'm assuming that the SINGLE raised flesh colored lesion is a Hamartoma (The angiofibromas in NF1 are typically multiple). Although both Tuberous Sclerosis and Sturge Weber are both associated with seizures, I used all the other stuff to narrow it down to the correct answer. Also, don't forget that there is Incomplete penetrance and variable expressivity in Tuberous Sclerosis. So I think the lack of family history of "seizure or major medical illness" was there to throw us off. +9  
bubbles  Thank you! :) I thought I really knew my congenital disorders, so I was a little annoyed when they trotted this question out +1  




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submitted by d_holles(31),

This video explains the pediatric neurocutaneous disorders well.

https://www.youtube.com/watch?v=Lom7tnK8HCk

Basically the key here is hypopigmented macules. NF1 has cafe au liate spots (hyperpigmented macules) while TSC has ash leaf spots (hypopigmented macules). This is a decode the buzzword style question. I felt like I didn't really understand these orders until I watched the above video.