Inclusion-cell (I-cell) disease, also referred to as Mucolipidosis II alpha/beta is part of the lysosomal storage disease family and results from deficiency of several lysosomal enzymes. The coding and translation of the genes for these enzymes is normal, however, they are not normally transported to the lysosomes from the endoplasmic reticulum because they lack a specific targeting signal. Without the proper functioning of N-acetylglucosamine-1-phototransferase, a build up of substances occur when enzymes are unable to travel inside of the lysosome.
Mucolipidosis II alpha/beta is a rare disorder, although its exact prevalence is unknown. It is estimated to occur in about 1 in 100,000 to 400,000 individuals worldwide. This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.