In fact, the majority of individuals with MPS-VI are currently screened by rather non-specific measurements of total urinary glycosaminoglycan levels (24–26), although the lack of Arsb, i.e. N-acetylgalactosamine-4-sulfatase, should cause a specific enrichment of 4-sulfated chondroitin and dermatan sulfates. The gene discussed is ARSB; the disease is mucopolysaccharidosis type 6.