Phenotypic spectrum and incidence of TRPV4 mutations in patients with inherited axonal neuropathy.

OBJECTIVE

To clarify the phenotypic spectrum and incidence of TRPV4 mutations in patients with inherited axonal neuropathies.

METHODS

We screened for TRPV4 mutations in 169 French unrelated patients with inherited axonal peripheral neuropathy. Ninety-five patients had dominant Charcot-Marie-Tooth type 2 (CMT2) disease, and 74 patients, including 39 patients with distal hereditary motor neuropathy, 14 with congenital spinal muscular atrophy and arthrogryposis, 13 with CMT2, and 8 with scapuloperoneal spinal muscular atrophy, presented with additional vocal cord paralysis and/or skeletal dysplasia.

RESULTS

No deleterious TRPV4 mutation was identified in the 95 patients with "pure" CMT2 (0/95). In contrast, 12 of 74 patients (16%) with neuropathy and vocal cord paralysis and/or skeletal dysplasia presented pathogenic TRPV4 mutations, including 7 patients with distal hereditary motor neuropathy, 2 with scapuloperoneal spinal muscular atrophy, 2 with congenital spinal muscular atrophy and arthrogryposis, and one with CMT2. Investigation of affected relatives allowed us to study 17 patients. All patients had childhood-onset motor neuropathy and showed a variety of associated findings, including foot deformities (100% of cases), kyphoscoliosis (100%), elevated serum creatine kinase levels (100%), vocal cord paralysis (94%), scapular winging (53%), respiratory insufficiency (29%), hearing loss (24%), skeletal dysplasia (18%), and arthrogryposis (12%). Eight missense mutations were observed in these 12 families, including 2 previously unreported. Six mutations were de novo events, and 2 asymptomatic carriers were identified.

CONCLUSION

With 16% of patients affected in our series, this study demonstrates that TRPV4 mutations are a major cause of inherited axonal neuropathy associated with a large spectrum of additional features.