MPS IVA is characterized by a deficiency of the lysosomal enzyme N-acetylgalactosamine-6-sulfatase (GALNS), which is required for the degradation of the glycosaminoglycans (GAGs), keratan sulfate (KS) and chondroitin-6-sulfate (CS) [1]. The gene discussed is GALNS; the disease is mucopolysaccharidosis type 4A.