GALNS and mucopolysaccharidosis: Morquio A syndrome, also called mucopolysaccharidosis (MPS) IVA, is an ultra-rare autosomal recessive lysosomal storage disorder caused by deficient activity of the enzyme N-acetylgalactosamine-6-sulfatase (GALNS; EC 3.1.6.4), involved in the catabolism of the glycosaminoglycans (GAGs) keratan sulfate (KS) and chondroitin-6-sulfate [1].