Charcot-Marie-Tooth Disease Type 1A — SCE Neurology MCQ

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HardNeurogeneticsCharcot-Marie-Tooth Disease Type 1ASCE Neurology

A family has autosomal-dominant demyelinating Charcot–Marie–Tooth disease with uniformly slow conduction velocities. Which genetic alteration is most likely?

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Correct answer: C — A PMP22 duplication causing CMT1A

The best answer is “A PMP22 duplication causing CMT1A”. The commonest demyelinating CMT subtype, CMT1A, is usually caused by a duplication encompassing PMP22 on chromosome 17; a deletion causes hereditary neuropathy with liability to pressure palsies. The alternatives “A PMP22 deletion causing pressure-palsy neuropathy”, “A GJB1 variant causing X-linked CMT”, “An MFN2 variant causing axonal CMT2A”, “A TTR variant causing amyloid polyneuropathy” are clinically adjacent possibilities, but they do not match the defining chronology, localisation, physiology, investigation result or UK management sequence in this stem.

Reference: NICE NG236 stroke rehabilitation recommendations: https://www.nice.org.uk/guidance/ng236/chapter/Recommendations