Pseudo-Hurler polydystrophy

Overview
Pseudo-Hurler polydystrophy, also referred to as mucolipidosis III (ML III), is lysosomal storage disease closely related to I-cell disease (ML II). Symptoms of ML III are often not noticed until the child is 3-5 years of age.

Pathophysiology
As in ML II, ML III results from genetic defects in GlcNAc phosphotransferase (N-acetylglucosamine-1-phosphotransferase). However, ML III produces less severe symptoms and progresses more slowly, probably because the defect in GlcNAc phosphotranspherase lies in its protein recognition domain. Therefore, the catalytic domain retains some of its activity, resulting in a smaller accumulation of carbohydrates, lipids, and proteins in the inclusion bodies.

Presentation
Patients with ML III are generally of normal intelligence (trait) or have only mild mental retardation. These patients usually have skeletal abnormalities, coarse facial features, short height, and corneal clouding. Some individuals with ML III survive until their fourth or fifth decade of life.