NBME 22 Tuberous sclerosis complex (NBME Answers)

Retired NBME 22 Answers

nbme22/Block 2/Question#50 (reveal difficulty score)
An 18-month-old boy is admitted to the ...
Tuberous sclerosis complex 🔍 / 📺 / 🌳 / 📖
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submitted by ∗d_holles(218)

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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.

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pg32 I figured this out for a few reasons. The hypopigmented patches are ashleaf spots and the raised, flesh-colored lesion on the back is a Shagreen patch (only seen in TSC). Multiple brain lesions = hamartomas. Additionally, NF1 has 100% penetrance, though it also has variable expressivity, meaning if it were NF1 we would probably see some family history of similar symptoms. +4

castlblack Agree. CAFESPOTS Cafe-au-lait, Axillary Freckles, Eye (Lisch nodules), Sarcoidosis, Pheo, Optic Tumor (glioma), Seizures +1

rockodude the video is very helpful +

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submitted by ∗bubbles(79)

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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...

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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. +19

bubbles Thank you! :) I thought I really knew my congenital disorders, so I was a little annoyed when they trotted this question out +8

pg32 @cocoxaurus I believe the single raised flesh-colored lesion is actually a Shagreen patch, which helps you arrive at TSC as the diagnosis. +2

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submitted by ∗armymed88(49)

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

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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"? +18

d_holles @fcambridge variable expressivity of TSC allows for many different phenotypes. +1

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submitted by ∗diabetes(31)

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i was hesitated between neurofibromatosis type1 and tuberous sclerosis ,the two have skin + brain lesions ,AD,but the first has 100% penetrance ,optic gliomas ,hperpigmented cafe-au-lait spots,no seizure,so seond is the answer.

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