However, a gain-of-function mutation in ClC-7, Y715C, was recently shown to cause a novel disease, featuring hypopigmentation, organomegaly, and developmental delay; in contrast to loss of function diseases, patients did not have osteopetrosis, but rather a constellation of symptoms including excessively acidic lysosomes, lysosome storage, and accumulated enlarged vacuoles in cells32, confirming a role in pH regulation. This evidence concerns the gene CLCN7 and osteopetrosis.