Distal Hereditary Motor Neuropathies: A Rare Familial Case Caused by a Mutation in the VWA1 Gene

Distal hereditary motor neuropathies (dHMN) include 7 categories according to the mode of transmission, age of onset, topography of the deficit, and presence of associated signs. Recently, the VWA1 gene has been identified as responsible for dHMN with autosomal recessive inheritance, manifesting by muscle weakness starting in childhood or adulthood. We report the case of a 50-year-old patient presenting with dHMN with a mutation of the VWA1 gene. The patient, the first born of non-consanguineous parents, presented with a lower limb deficit initially diagnosed as spinal muscular atrophy (SMA). His sister has also motor neuropathy since childhood. Symptoms began early, with delayed acquisition of sitting and walking. Clinical examination revealed a disto-proximal deficit in all four limbs, predominating in the lower limbs, a discrete static cerebellar syndrome, and asymmetric dysmetria. Diffuse amyotrophy of the legs persisted, particularly in the tibialis anterior. Electroneuromyogram confirmed distal motor neuropathy, and muscles MRI showed symmetrical fatty degeneration of the muscles, marked in the pelvis and distal lower limbs. The genetic panel excluded proximal SMA and the classic mutations of peripheral neuropathies. A homozygous variation in the VWA1 gene (NM_022834.5:c.62_71dup) was identified, confirming the diagnosis of dHMN linked to this gene. Conclusion: This case illustrates the genetic variability of dHMN and the importance of extending genetic analyses to include emerging mutations such as those in the VWA1 gene. Keywords: neuropathies, hereditary, gene.