Mucopolysaccharidosis type IVA (MPS IVA, also called Morquio syndrome type A) is a rare autosomal recessive disorder caused by mutations in the GALNS gene, which encodes N-acetylgalactosamine-6-sulfatase (EC 3.1.6.4). The gene discussed is GALNS; the disease is mucopolysaccharidosis type 4A.