GALNS and mucopolysaccharidosis type 4A: Mucopolysaccharidosis IV A (MPS IVA, Morquio-A syndrome, OMIM#253,000) is an autosomal recessive disorder which is caused by the deficiency in enzyme activity of N-acetylgalactosamine-6-sulfate sulfatase (GALNS) due to biallelic variants in the GALNS gene (OMIM#612,222) [1, 2].