HNPP – PMP22 Deletion — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularHNPP – PMP22 DeletionSCE Neurology

A 35-year-old man with hereditary neuropathy with liability to pressure palsies (HNPP) presents with recurrent episodes of painless focal neuropathies at compression sites. NCS show diffuse slowing at common entrapment sites. What is the genetic basis of HNPP?

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Correct answer: C — PMP22 deletion on chromosome 17

HNPP is caused by a heterozygous deletion of the PMP22 gene on chromosome 17p11.2 (the reciprocal of the PMP22 duplication that causes CMT1A). It follows autosomal dominant inheritance and presents with recurrent, painless, episodic focal neuropathies triggered by minor trauma or compression (peroneal palsy, ulnar neuropathy, carpal tunnel). NCS show diffuse conduction slowing, particularly at entrapment sites, even in asymptomatic nerves. A: PMP22 duplication causes CMT1A. C: MFN2 mutations cause CMT2A. D: GJB1 mutations cause CMTX1. E: MPZ mutations cause various CMT subtypes.

Reference: EAN/PNS CMT Guidelines; ABN Inherited Neuropathy Guidelines