Mucopolysaccharidosis Type II


What is mucopolysaccharidosis type II (MPS II) disease?

Mucopolysaccharidosis type II, also known as Hunter syndrome and MPS II, is a progressive (disease that gets worse with time) X-linked genetic syndrome in the category of lysosomal storage diseases that primarily affects boys. Rarely, girls have also been diagnosed with this disease. Hunter disease was first described in 1917 by Dr. Charles Hunter, a physician in Canada overseeing the care of two brothers with the disorder.

Individuals with MPS II are missing an enzyme called iduronate 2-sulfatase or I2S and are not able to break down sugar molecules called glycosaminoglycan (GAG) in their cells to smaller molecules. Due to the missing I2S enzyme, dermatan sulfate and heparan sulfate (GAGs) build up in a compartment of the cell called the lysosome causing the symptoms and features of MPS II. GAGs are long chains of sugar molecules the body needs for building bones, cartilage, skin, tendons and other types of tissues.

As the disease progresses, other organs and tissues are effected by the build up of GAGs. The brain, heart and skeletal system are the major organs affected in MPS II, as well as problems with breathing due to blocked or restricted airways. The storage of GAGs is found in almost all cell types within the body.

MPS II, like other MPS disorders, has a wide spectrum of disease symptoms. There are two major types of MPS II, the early progressing type and the slowly progressive type. One of the major differences between these two types of MPS II is how the brain is effected by the disease. In the early progressing type, individuals may experience regression or loss of milestones and cognitive development between 6 to 8 years of age, and pass away by 20 years of age. In the slowly progressing type, cognitive abilities may be in the normal range and individuals may live into adulthood.

The best person to figure out if someone may have MPS II is a geneticist (doctor with special training in genetics), or other doctor with special training and experience in lysosomal storage disorders and MPS. You can ask your primary doctor for a referral or recommendation. The American College of Medical Genetics and Genomics (ACMG) also has a "Find a Genetics Clinic" search function that can help you find a genetics specialist near you. ACMG Find a Genetic Service

There are 11 different types of mucopolysaccharidosis with many overlapping signs and symptoms. Early and accurate diagnosis is important.

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