CMT Type 2A – Axonal Neuropathy — SCE Neurology MCQ

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ModeratePeripheral Neuropathy & NeuromuscularCMT Type 2A – Axonal NeuropathySCE Neurology

A 30-year-old man presents with a 3-year history of bilateral foot weakness (foot drop), distal leg wasting, and mild sensory loss in a stocking distribution. NCS show reduced CMAP and SNAP amplitudes with normal conduction velocities. His father has similar symptoms. Genetic testing shows a mutation in the MFN2 gene. What type of CMT does he have?

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Correct answer: B — CMT type 2A (axonal)

CMT type 2A is the most common axonal form of Charcot-Marie-Tooth disease, caused by mutations in the MFN2 (mitofusin 2) gene. It is autosomal dominant and characterised by distal weakness and wasting with mild sensory involvement. NCS show an axonal pattern (reduced CMAP and SNAP amplitudes with normal or near-normal conduction velocities), distinguishing it from CMT1A which has severely slowed conduction velocities. A: CMT1A has severely slowed CVs (<38 m/s) due to PMP22 duplication. C: CMT X1 has GJB1 mutations with intermediate CVs. D: HNPP has PMP22 deletion with episodic neuropathies. E: Dejerine-Sottas (CMT3) has very slow CVs and severe early-onset neuropathy.

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