II is a rare inherited
metabolic disorder characterized by coarse facial
features, skeletal abnormalities and mental retardation
. The symptoms of I-cell disease are similar to but more severe than those of Hurler syndrome. The symptoms associated with this disorder typically become obvious during infancy and may include multiple abnormalities of the skull and face and growth delays.
This disorder belongs to a group of diseases known as lysosomal storage
disorders. Lysosomes are particles bound in membranes within cells that break down certain fats and carbohydrates. Multiple enzyme deficiencies associated with I-cell disease lead to the accumulation of certain fatty substances (mucolipids) and certain complex carbohydrates (mucopolysaccharides) within the cells of many tissues of the body.
I-cell disease is caused by a mutation in the GNPTA gene that leads to a deficiency in the enzyme UDP-N-acetylglucoseamine-1-phosphotransferase. I-cell disease is inherited as an autosomal recessive genetic trait.