Mucopolysaccharidosis type IIIA (MPS IIIA) is caused by the functional defect of N-sulfoglucosamine sulfohydrolase (SGSH; also known as sulfamidase, sulfamate sulfohydrolase and heparan N-sulfatase; EC 3.10.1.1) and represents one of the most frequent lysosomal storage diseases worldwide. The gene discussed is SGSH; the disease is lysosomal storage disease.