Clinical Utility

The mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by a deficiency of lysosomal enzymes catalyzing the degradation of glycosaminoglycans (GAG) (mucopolysaccharides). Depending on the enzyme deficiency, the catabolism of dermatan sulfate, heparan sulfate, keratan sulfate, chondroitin sulfate, or hyaluronan, may be blocked singly or in combination. Lysosomal accumulation of GAG molecules results in cell, tissue, and organ dysfunction. The MPSs share many clinical features, although in variable degrees. The disorders are chronic and progressive, and usually display a wide spectrum of clinical severity within one enzyme deficiency. GAG fragments generated by alternative pathways are excreted in urine, providing the basis for diagnostic screening for the MPS. Urine values are expressed as a GAG/creatinine ratio as well as mg/L. Both are typically elevated in patients with storage disease, however, patients with Morquio have been known to have normal excretion. In patients who have had bone marrow transplant, CSF may be assayed to assess the efficacy of the treatment on the central nervous system.