MPSIIIB is caused by a deficiency in α-N-acetylglucosaminidase (NAGLU), MPSIIIC by acetyl–CoA:α-glucosaminide N-acetyltransferase (HGSNAT) deficiency and MPSIIID by N-acetylglucosamine 6-sulfatase deficiency1,2. Here, NAGLU is linked to mucopolysaccharidosis type 3D.