Late-Onset, Autosomal Dominant, Axonal, Sensorimotor Neuropathy Due to the New Variant c.1A_G in Myelin Protein Zero (MPZ): A Case Report.

To the best of our knowledge, autosomal dominant Charcot-Marie-Tooth disease type 1B (CMT1B) due to the c.1A>G variant in myelin protein zero (MPZ) has not yet been reported. The patient was a 56-year-old man with slowly progressive atrophy of the distal muscles of the lower limbs that started in his forties. He later developed transient numbness in both feet. One year before presentation, he noticed paresthesia in the distal lower limbs and easy fatigability when walking uphill. His family history revealed hereditary neuropathy in his mother and her two sisters. Genetic testing of his mother and an aunt revealed the new variant c.1A>G in MPZ (p.Met1Val). Clinical neurological examination revealed myopia, hypoacusis, absent tendon reflexes on the upper and lower limbs, mild weakening of the left thumb and right foot extensors, hypoesthesia and hypoalgesia on both soles and dorsum of the feet, and mild pallhypesthesia on the lower limbs. Nerve conduction studies (NCS) revealed severe sensorimotor axonal neuropathy. The index patient also carried the mutation identified in his mother and aunt. The MPZ variant c.1A>G manifests phenotypically with late-onset CMT1B. Neurologists should be aware that hereditary neuropathy can have a late onset and a slowly progressive course over a number of years, with the ability to walk unimpaired into old age.