Assays / Genetic Enzymes / I-Cell Disease and Pseudo-Hurler Polydystrophy

These diseases are also called mucolipidosis type II and mucolipidosis type III, respectively. There are similar biochemical abnormalities in both but differing clinical severity. In I-cell disease there is similarity to Hurler disease, with similar facies, restriction of joint movement, hepatosplenomegaly and progressive psychomotor retardation. Similar radiological skeletal changes are seen. Death usually occurs by 5 years of age. Pseudo-Hurler polydystrophy patients usually present at 2-4 years with resemblance to a mild mucopolysaccharidosis. There is stiffness of the shoulder and hands, later leading to claw-hand deformity, mild facial coarsening, carpal tunnel syndrome and cardiac valvular disease. Intelligence is usually, but not always, reduced.

Enzyme Test: Very high levels of arylsulphatase A are seen in serum and plasma in these diseases. There is also elevation of a-mannosidase, b-hexosaminidase and several other lysosomal enzymes in serum and plasma and deficiency in cultured fibroblasts. The effects are not seen in white blood cells.

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