Sulfatases are enzymes that hydrolyse a diverse range of sulfate esters. Deficiency of lysosomal sulfatases leads to human diseases characterized by the accumulation of either GAGs (glycosaminoglycans) or sulfolipids. Sulfamidase, also known as HSS, SFMD, MPS3A or SGSH, is a 502 amino acid lysosome that belongs to the sulfatase family. It has been suggested that sulfamidase may be involved in the lysosomal degradation of heparan sulfate. Defects in the gene encoding sulfamidase are the cause of