GALNS and mucopolysaccharidosis type 4A: Mucopolysaccharidosis IV A (MPS IV A, Morquio A disease, OMIM 253000) is a lysosomal storage disease (LSD) produced by mutations on N-acetylgalactosamine-6-sulfate sulfatase (GALNS, EC 3.1.6.4), leading to the lysosomal accumulation of keratan- and chondroitin-sulfate1, 2.