NORD gratefully acknowledges Robert J. Desnick, PhD, MD, Dean for Genetics and Genomics, Professor and Chair, Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, for assistance in the preparation of this report.
Schindler disease is a rare inherited metabolic disorder characterized by the deficient activity of the lysosomal enzyme alpha-N-acetylgalactosaminidase (alpha-NAGA or alpha-galactosidase B). The enzyme defect leads to the abnormal accumulation of certain complex compounds (glycosphingolipids, glycoproteins, and oligosaccharides), which have terminal or preterminal N-acetylgalactosaminyl residues in many tissues of the body and in urine. Two major forms of Schindler disease exist - a severe form with onset in infancy (type I) and a milder form with onset in adulthood (type II). Some researchers have proposed a type III form of Schindler disease that is less severe than type I, but more severe than type II. The specific symptoms and severity of Schindler disease can vary from one person to another. Schindler disease is caused by mutations of the NAGA gene and is inherited as an autosomal recessive trait.
Schindler disease belongs to a group of diseases known as lysosomal storage disorders. Within cells, lysosomes are small compartments or organelles which are bound by membranes. They function as the primary digestive units of cells. Enzymes within lysosomes break down or digest particular nutrients and cellular debris. Low levels or inactivity of these enzymes leads to the abnormal accumulation of the substances that they normally breakdown, resulting in the enlargement and increased numbers of lysosomes within cells of the body, as well as leakage of their stored contents. These disturbances may interfere with normal cellular function and cause the disease manifestations.
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