SMPX and Skeletal myopathy: SMPX is also expressed in the hair cells of the inner ear [13, 34, 36], and variants causing a loss-of-function cause hereditary progressive non-syndromic hearing loss (NSHL, OMIM 300066) [1, 3, 7, 13, 22, 27, 28, 36] without reported skeletal myopathy.