What Is Mucopolysaccharidosis?

Mucopolysaccharidosis is a collection of metabolic disorders that arise when mucopolysaccharides are unable to break down, causing a fault in the production of a particular gene. This results in abnormalities of specific enzymes. Mucopolysaccharidosis includes disorders such as Hurler’s, Hunter’s Maroteaux-Lamy and Sanfilippo syndromes. It also includes Morquion, Sly and Scheie’s syndromes. Such metabolic disorders affect an average of one child in every 10,000 and usually result in death before the child becomes an adult.

Being a group of genetic disorders, mucopolysaccharidosis is distinguished by an accumulation of mucopolysaccharides in tissues. Mucopolysaccharides are sugar molecules that look like long chains under a microscope and are used throughout the body to build connective tissue. Many of the body’s structures are held together by connective tissue, making it the most abundant and necessary tissue in the body. Mucopolysaccharidosis involves a defect in gene production related to the metabolism of or the processing of mucopolysaccharides, resulting in a buildup of these molecules.

Specific mucopolysaccharides are involved in the development of mucopolysaccharidosis. These include heparan sulfate, dermatan sulfate or keratan sulfate. If there is a problem with the processing of any one of these mucopolysaccharides, an abnormality could occur on the enzymes that are associated with these metabolic pathways.

Each syndrome has its own characteristics, depending on which particular enzyme or combination of enzymes is affected by a faulty gene. Hurler’s syndrome, also known as gargoylism, is the most common form of mucopolysaccharidosis, and it occurs when there is a deficiency of the enzyme alpha-L-iduronidase. Hurler’s syndrome is characterized by growth retardation, distorted facial features, deficiencies in mental functioning, deafness, stiff joints and deformities of the chest. It also is characterized by enlargement of the liver and spleen as well as cornea deficits that affect eye functioning.

Mucopolysaccharidosis disorders are progressive and result in both physical and structural deformities. Each disorder has differing levels of severity, and symptoms commonly begin to appear after a child is 2 years old. Children who have any form of this disorder usually will live no more than 20 years. In most cases, children do not reach their teenage years.

Diagnosis is made after testing for enzyme deficiencies that are involved in metabolic pathways and after examining whether there is an accumulation of polysaccharides in connective tissue. There is no cure for mucopolysaccharidosis. Treatment has involved bone marrow transplants in an attempt to restore deficient enzymes, but this has had little success. More attention has been placed on improving diagnosis and detecting whether parents are carriers for the different traits.