[MIM*252900, MIM*252920, MIM*252930,] an error of the mucopolysaccharide metabolism, with excretion of large amounts of heparan sulfate in the urine; characterized by severe mental retardation with hepatomegaly; skeleton may be normal or may present mild changes similar to those in Hurler syndrome; several different types (A, B, C, and D) have been identified according to the enzyme deficiency; autosomal recessive inheritance. SYN: mucopolysaccharidosis type III.