TRPV4 and proximal spinal muscular atrophy: Scapuloperoneal spinal muscular atrophy (SP-SMA), congenital distal spinal muscular atrophy (CDSMA), congenital spinal muscular atrophy and arthrogryposis (CSMAA), hereditary motor and sensory neuropathy type I1C (HMSN IIC), and Charcot–Marie–Tooth disease type 2C (CMT 2C) are caused by a heterozygous mutation in the transient receptor potential vanilloid 4 (TRPV4) gene located on chromosome 12q24.