Mucopolysaccharidosis type IIIA (MPS-IIIA) is a form of Sanfilippo syndrome resulting from a deficiency in functional N-sulfoglucosamine sulfohydrolase (SGSH, EC:3.10.1.1)—an enzyme involved in degradation of heparan sulfate [6,7]. The gene discussed is SGSH; the disease is mucopolysaccharidosis type 3A.