Myotonia congenita, leukodystrophy, Bartter syndrome, Dent’s disease, and osteopetrosis/retinal degeneration/lysosomal storage disease have well-established association with loss-of-function of ClC1, ClC-2, ClC-K/Barttin, ClC-5 and ClC-7/Ostm1, respectively. The gene discussed is CLCN7; the disease is retinal degeneration.