GALNS and mucopolysaccharidosis type 4A: Morquio A syndrome (mucopolysaccharidosis IVA [MPS IVA]; OMIM #253000) is an autosomal recessive lysosomal storage disorder caused by deficiency in the enzyme N-acetylgalactosamine-6-sulfatase (GALNS; EC 3.1.6.4), resulting in impaired degradation of the glycosaminoglycans (GAGs) keratan sulfate (KS) and chondroitin-6-sulfate.