GALNS and lysosomal storage disease: MPS-IVA is a lysosomal storage disorder caused by mutations in the GALNS gene (NM_000512.5), which leads to a deficiency of the enzyme N-acetyl-galactosamine-6-sulfate sulfatase (GALNS) and the accumulation of glycosaminoglycans (GAG) keratan sulfate and chondroitin 6-sulfate.