GALNS and mucopolysaccharidosis type 4A: Morquio A syndrome (or Mucopolysaccharidosis IVA) is a lysosomal storage disorder caused by the deficiency of the lysosomal enzyme N-acetylgalactosamine 6-sulfatase (GALNS, EC 3.1.6.4) that leads to the accumulation of two glycosaminoglycans (GAGs), keratan sulphate and chondroitin 6-sulphate, within lysosomes [8,9,10,11].