Health Information

I-cell disease (mucolipidosis 2) and pseudo-Hurler polydystrophy (mucolipidosis 3) are related diseases that arise from defects in Lysosomal enzyme targeting because of a deficiency in the enzyme that transfers N-acetyglucosamine phosphate to the high-mannose type oligosaccharides of proteins destined for the lysosome.

Fibroblasts in vitro from affected individuals show dense inclusion bodies (hence I-cells) and are defective in multiple Lysosomal enzymes that are found secreted into the medium. Patients have abnormally high levels of Lysosomal enzymes in their sera and other body fluids. The disease is characterized by severe psychomotor retardation, many skeletal abnormalities, coarse facial features, and restricted joint movement. Symptoms are usually observable at birth and progress until death, usually by age 8. Pseudo-Hurler polydystrophy is a much milder form of the disease. Onset is usually delayed until the age of 2-4 years, the disease progresses more slowly, and patients survive into elder hood. Prenatal diagnosis of both diseases is possible, but there is as yet no definitive treatment.