Inclusion-cell disease

Inclusion-cell disease, also called I-cell disease or mucolipidosis II, is a lysosomal storage disease caused by a defective phosphotransferase enzyme in the Golgi apparatus. The enzyme normally tags certain proteins with mannose-6-phosphate so they are routed to lysosomes. Without the tag, lysosomal enzymes are secreted from the cell instead, and the lysosomes fill with undegraded material, producing the characteristic inclusion cells seen under the microscope. It is an autosomal recessive disorder linked to a deficiency of GlcNAc phosphotransferase. Signs usually show by six months, with failure to thrive, developmental delay, coarse facial features, restricted joint movement, enlarged liver and spleen, corneal clouding and short-trunk dwarfism, and the picture resembles Hurler syndrome. Children often die before the age of seven from heart failure or respiratory infection. There is no cure, and treatment is limited to controlling symptoms, though bone marrow transplant may delay neurological decline.