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Mucopolysaccharidoses (MPS) are characterized by mental retardation constantly present in the severe forms of Hurler (MPS I), Hunter (MPS II) and Sanfilippo (MPS III) diseases. On the contrary, mental retardation is absent in Morquio (MPS IV) and Maroteaux-Lamy (MPS VI) diseases and absent or only minimal in the attenuated forms of MPS I, II and III. Considering that MPS patients affected by mental disease accumulate heparan sulfate (HS) due to specific enzymatic defects, we hypothesized a possible correlation between urinary HS-derived glucosamine (GlcN) accumulated in tissues and excreted in biological fluids and mental retardation. 83 healthy subjects were found to excrete HS in the form of fragments due to the activity of catabolic enzymes that are absent or impaired in MPS patients. On the contrary, urinary HS in 44 patients was observed to be composed of high molecular weight polymer and fragments of various lengths depending on MPS types. On this basis we correlated mental retardation with GlcN belonging to high and low molecular weight HS. We demonstrate a positive relationship between the accumulation of high molecular weight HS and mental retardation in MPS severe compared to attenuated forms. This is also supported by the consideration that accumulation of other GAGs different from HS, as in MPS IV and MPS VI, and low molecular weight HS fragments do not impact on central nervous system disease.

Dyggve-Melchior-Clausen (DMC) syndrome is a rare autosomal recessive disorder affecting skeletal development. The patients have a striking "barrel-shape" chest, shortened trunk, and various distal deformities, including genu valgum or varum, and minimal decrease in joint mobility. The most notable radiographic findings are a lacy iliac crest apophysis, hip dysplasia, double vertebral hump, and odontoid hypoplasia with atlanto-axial instability. Patients may require orthopedic femoral osteotomy, total hip arthroplasty, early meniscectomy, realignment osteotomy, or posterior cervical spine fusion. Patients with the Smith McCort variant have similar orthopaedic manifestations but are not mentally retarded. The diagnosis may be confirmed histologically, but no biochemical or developmental defect has been defined as yet. The authors report seven affected members of two families from Guam and describe their orthopaedic treatment. The authors review the historical reports, clinical findings, and diagnostic radiographic features in DMC syndrome.

An eight year old boy of first grade consanguinity parents, with important growth and mental retardation, generalized bone alterations and without corneal opacity nor mucopolysacchariduria is presented. All these features account on the syndrome of Dyggve-Melchior and Clausen.

This report describes 7 patients, aged 30 to 43 years, suffering from a mild variant of Sanfilippo B-disease. Somatic findings in these patients are unremarkable. Dementia and behavioral disturbances occurred late in the course of the disease. All 7 patients were examined 10 years previous to this study and reported in earlier publications [van de Kamp et al, 1976, 1981].

Cultured skin fibroblasts from two patients with Sanfilippo syndrome, Type B were strikingly deficient in alpha-acetylglucosaminidase activity (alpha-2-acetamido-2-deoxy-D-glucoside acetamidodeoxyglucohydrolase, EC 3.2.1.X). A similar deficiency was found in frozen organs from two other patients. A partial deficiency of alpha-acetylglucosaminidase was found in cultured skin fibroblasts from both parents of one patient. Soluble endogenous inhibitors did not account for the enzyme deficiency. Other lysosomal hydrolases were normal or increased in cultured fibroblasts from patients with this disease. No deficiency of alpha-acetylglucosaminidase is present in other genetic mucopolysaccharidoses, including Sanfilippo Type A.