Morquio disease or Mucopolysaccharidosis Type IV (MPS IV) belongs to this group and has two sub-types, A and B. Type A is also known as Morquio A, GALNS deficiency, Galactosamine-6-sulfatase deficiency, N-acetylgalactosamine-6-sulfate sulfatase deficiency or more simply MPS IVA, while type B is known as Morquio B, beta-galactosidase deficiency or MPS IVB. Here, GALNS is linked to mucopolysaccharidosis type 4A.