GALNS and lysosomal storage disease: <h4>Background</h4>Morquio A syndrome, mucopolysaccharidosis type IVA (MPS IVA), is a lysosomal storage disorder caused by the deficient activity of N-acetylgalactosamine-6-sulfatase (GalNac6S), due to alterations in the <i>GALNS</i> gene.