Mental retardation is NOT a feature of one of the mucopolysaccaridos

Mucopolysaccharidoses (MPS) The MPSs are a group of closely related syndromes that result from genetically determined deficiencies of enzymes involved in the degradation of mucopolysaccharides (glycosaminoglycans). Chemically, mucopolysaccharides are long-chain complex carbohydrates that are linked with proteins to form proteoglycans. They are abundant in the ground substance of connective tissue. The glycosaminoglycans that accumulate in MPSs are dermatan sulfate, heparan sulfate, keratan sulfate, and chondroitin sulfate. The enzymes involved in the degradation of these molecules cleave terminal sugars from the polysaccharide chains disposed along a polypeptide or core protein. In the absence of enzymes, these chains accumulate within lysosomes in various tissues and organs of the body. Several clinical variants of MPS, classified numerically from MPS I to MPS VII, have been described, each resulting from the deficiency of one specific enzyme. All the MPSs except one are inherited as autosomal recessive traits; the exception, Hunter syndrome, is an X-linked recessive trait. Within a given group (e.g., MPS I, characterized by a deficiency of a-l-iduronidase), subgroups exist that result from different mutant alleles at the same genetic locus. Thus, the severity of enzyme deficiency and the clinical picture even within subgroups are often different. In general, MPSs are progressive disorders, characterized by coarse facial features, clouding of the cornea, joint stiffness, and mental retardation. Urinary excretion of the accumulated mucopolysaccharides is often increased. Ref Robbins 9/e pg 154