The mucopolysaccharidoses are a group of inherited metabolic disorders that result from a deficiency of enzymes required for the breakdown of intracellular molecules. Charles Hunter, a Canadian internist first described this type in two brothers in the 1950s.
Individuals with this disorder may be diagnosed as early as 2 years of age when children present with an enlarged liver and spleen together with evidence of developmental delays. They are often short in stature with a coarse facies, short neck, barrel chest and a prominent abdomen. The joints may be stiff and the skull is often enlarged. There is a wide range of clinical disease and many patients are only mildly affected with normal intelligence while others have severe breathing and heart problems. Hearing loss and behavior problems are often present.
This disorder is caused by a mutation in a gene on the X-chromosome and therefore occurs primarily in males. Rare females who are affected may have loss of DNA from the X-chromosome instead of a simple gene mutation. Females who carry the mutation can expect that half of their sons and none of their daughters will inherit type II mucopolysaccharidosis.
This disorder is usually diagnosed by pediatricians early in life although mild cases may not come to attention until later. One form is considered to be associated with more severe disease, more rapid progress and death may occur in adolescence, often from respiratory and cardiac complications. The more mild form does not progress as rapidly and is compatible with life into the seventh decade. Patients with the latter form usually have normal intelligence.
Various forms of treatment are under investigation, including bone marrow transplantation and enzyme replacement therapy. Early indications suggest these treatments may be helpful but more study is necessary.