GALNS and mucopolysaccharidosis type 4A: MPS IVA or Morquio A syndrome (253000) is an autosomal recessive MPS disorder caused by deficiency of the N-acetylgalactosamine-6-sulfatase (GALNS) enzyme (EC 3.1.6.4), which impairs lysosomal degradation of keratan sulphate and chondroitin-6-sulphate [7–11].