GALNS and mucopolysaccharidosis type 4: Mucopolysaccharidosis IV-A or Morquio A disease (MIM #253000] is an autosomal recessive lysosomal storage disease caused by the deficiency of N-acetylgalactosamine-6-sulfatase (GALNS), the lysosomal enzyme responsible for the hydrolytic degradation of keratan sulfate and chondroitin-6-sulfate [1].