GALNS and mucopolysaccharidosis type 4A: Mucopolysaccharidosis type IVA (MPS IVA) or Morquio Syndrome A (OMIM #253000) is an autosomal recessive lysosomal storage disorder caused by mutations in the GALNS gene, encoding N‐acetylglucosamine‐6‐sulfate sulfatase enzyme (EC 3.1.6.4).