Overview Of Mucopolysaccharidosis Type II
Mucopolysaccharidosis type II (MPS II) is a rare disease in which the body is missing or does not have enough of an enzyme needed to break down long chains of sugar molecules. These chains of molecules are called glycosaminoglycans (formerly called mucopolysaccharides). As a result, the molecules build up in different parts of the body and cause various health problems.
The condition belongs to a group of diseases called mucopolysaccharidoses (MPSs). MPS II is also known as Hunter syndrome.
There are several other types of MPS’s, including:
- MPS I (Hurler syndrome; Hurler-Scheie syndrome; Scheie syndrome)
- MPS III (Sanfilippo syndrome)
- MPS IV (Morquio syndrome)
Commonly Associated With
Alpha-L-iduronate deficiency; Mucopolysaccharidosis type I; Severe MPS I; Attenuated MPS I; MPS I H; MPS I S; Hurler syndrome; Scheie syndrome; Hurler-Scheie syndrome; MPS 1 H/S; Lysosomal storage disease – mucopolysaccharidosis type I
Causes Of Mucopolysaccharidosis Type II
MPS II is an inherited disorder. This means it is passed down through families. The affected gene is on the X chromosome. Boys are most often affected because they inherit the X chromosome from their mothers. Their mothers do not have symptoms of the disease, but they carry a nonworking copy of the gene.
MPS II is caused by a lack of the enzyme iduronate sulfatase. Without this enzyme, chains of sugar molecules build up in various body tissues, causing damage.
The early-onset, severe form of the disease begins shortly after age 2. A late-onset, mild form causes less severe symptoms to appear later in life.
Symptoms Of Mucopolysaccharidosis Type II
In the early-onset, severe form, symptoms include:
- Aggressive behavior
- The mental function gets worse over time
- Severe intellectual disability
- Jerky body movements
- In the late (mild) form, there can be mild to no mental deficiency.
In both forms of mucopolysaccharidosis type II, symptoms include:
- Carpal tunnel syndrome
- Coarse features of the face
- Deafness (gets worse over time)
- Increased hair growth
- Joint stiffness
- Large head
Exams & Tests
A physical exam and tests formucopolysaccharidosis type II may show:
- Abnormal retina (back of the eye)
- Decreased iduronate sulfatase enzyme in blood serum or cells
- Heart murmur and leaky heart valves
- Enlarged liver
- Enlarged spleen
- Hernia in the groin
- Joint contractures (from joint stiffness)
Tests for mucopolysaccharidosis type II may include:
- Enzyme study
- Genetic testing for a change in the iduronate sulfatase gene
- Urine test for heparan sulfate and dermatan sulfate
Treatment Of Mucopolysaccharidosis Type II
The medicine called idursulfase (Elaprase), which replaces the enzyme iduronate sulfatase may be recommended. It is given through a vein (IV, intravenously). Talk to your health care provider for more information.
Bone marrow transplant has been tried for the early-onset form, but the results can vary.
Each health problem caused by this disease should be treated separately.