Glossary

Arylsulfatase B. The enzyme, also known as N-acetylgalactosamine 4-sulfatase, that is deficient in MPS VI. This enzyme normally works in the lysosome to degrade the glycosaminoglycan dermatan sulfate.

Autosomal recessive. The manner in which MPS VI and most other lysosomal storage diseases are inherited. In order to develop MPS VI disease, an individual must inherit two defective copies of the gene for arylsulfatase B—one from each parent.

Carrier. An individual who possesses one defective copy and one normal copy of an autosomal recessive disease gene—in the case of MPS VI, for example, one defective copy of the gene for arylsulfatase B. Individuals who inherit only one defective copy of the arylsulfatase B gene possess enough enzyme activity to remain healthy.

Dermatan sulfate (DS). The substrate which accumulates in the tissues of patients with MPS VI. Dermatan sulfate is a glycosaminoglycan (GAG) which is normally present in a variety of tissues, including but not limited to the skin, heart valves, airways, and skeleton.

Dysostosis multiplex. The constellation of widespread skeletal and radiographic abnormalities seen in MPS disease.

Enzyme replacement therapy (ERT). The latest development in the treatment of certain conditions that arise when the body does not produce enough of an enzyme (see enzyme). In enzyme replacement therapy, the body is supplied with a replacement for the enzyme that it cannot produce. The replacement enzyme is biochemically identical to the deficient enzyme and thus is believed to perfom the exat same function. ERT has shown positive results in the treatment of certain diseases: Gaucher type 1, Fabry, MPS I, MPS II, and MPS VI. ERT can impact the progression of a disease that is cuased by a deficient enzyme. Clich here to learn more about ERT.

Fabry disease. A lysosomal storage disease caused by an enzyme deficiency and subsequent buildup of glycolipids. Fabry disease is one of several lysosomal storage diseases for which a specific treatment is already available.

Gaucher disease. A lysosomal storage disease caused by an enzyme deficiency and subsequent glycosphingolipid buildup. Gaucher disease is one of several lysosomal storage diseases for which specific treatments are already available.

Glycosaminoglycan (GAG). Also called mucopolysaccharide. A class of polysaccharides, including chondroitin, dermatan, keratan, and heparan, which are found in many connective tissues throughout the body. Pathologic accumulation of specific GAGs—caused by specific enzyme deficiencies—underlies the various forms of mucopolysaccharidosis, or MPS.

Hepatomegaly. Pathologic enlargement of the liver, as often occurs in lysosomal storage diseases such as MPS I, MPS VI, and Gaucher disease, due to accumulation of excess substrate.

Lysosomal storage disease. Any of a number of inherited genetic diseases in which individuals are deficient for one of the enzymes that are normally present in the lysosome. Owing to that enzyme deficiency, some cellular component—the substrate that the enzyme normally degrades—builds up in the lysosomes, leading eventually to a wide range of symptoms.

Lysosomes. Intracellular, membrane-enclosed compartments in which many cellular molecules such as polysaccharides and glycosphingolipids are degraded by specialized enzymes into their constituent parts (such as monosaccharides) which can then reenter cellular metabolism.

Maroteaux-Lamy syndrome. Another name for mucopolysaccharidosis VI (MPS VI). For more information, see MPS VI.

MPS I. Mucopolysaccharidosis I, also known as Hurler syndrome, Hurler-Scheie syndrome, or Scheie syndrome, depending on severity. MPS I is a lysosomal storage disease caused by an inherited autosomal recessive deficiency in the enzyme alpha-L-iduronidase. MPS I is one of the lysosomal storage diseases for which enzyme replacement therapy is available.

MPS II. Mucopolysaccharidosis II, also known as Hunter syndrome. MPS II is a lysosomal storage disease caused by an X-linked recessive inherited deficiency in the enzyme iduronate sulfatase.

MPS VI. Mucopolysaccharidosis VI, also known as Maroteaux-Lamy syndrome. MPS VI is a lysosomal storage disorder caused by an autosomal recessive inherited deficiency in the enzyme arylsulfatase B.

Mucopolysaccharidosis (MPS). A family of 7 lysosomal storage diseases, each one caused by a deficiency in a specific enzyme that degrades glycosaminoglycans, or GAGs (formerly called mucopolysaccharides). One type of MPS—MPS III—arises from a deficiency in any of 4 different enzymes, while another type—MPS IV—arises from a deficiency in either of 2 different enzymes.

N-acetylgalactosamine 4-sulfatase. See arylsulfatase B.

Organomegaly. Pathologic enlargement of organs such as the liver or spleen, as often occurs in lysosomal storage diseases such as MPS I, MPS VI, and Gaucher disease, due to accumulation of excess substrate.

Splenomegaly. Pathologic enlargement of the spleen, as often occurs in lysosomal storage diseases such as MPS I, MPS VI, and Gaucher disease, due to accumulation of excess substrate.