Mucopolysaccharidosis Type II (MPS II Hunter syndrome)
Description
Hunter syndrome, also known as mucopolysaccharidosis type II (MPS II), is a rare genetic disorder primarily affecting boys. It‘s caused by a deficiency of the enzyme iduronate-2-sulfatase, leading to a buildup of complex sugars in the body. This accumulation causes various health issues, impacting physical development, cognitive function, and overall well-being. This blog post delves into the intricacies of Hunter syndrome, exploring its signs, causes, diagnosis, management, and the importance of community support.
Genes Involved
Hunter syndrome is caused by mutations in the IDS gene, located on the X chromosome. This gene provides instructions for producing the iduronate-2-sulfatase enzyme.
Recognizing the Signs and Symptoms
Hunter syndrome presents a wide range of symptoms, with severity varying greatly between individuals. Some common signs include:
- Delayed development: Slowed growth, delayed walking or talking, and intellectual disability are often observed.
- Facial features: Coarse facial features, a prominent forehead, a broad nose, and a large tongue are characteristic.
- Skeletal abnormalities: Joint stiffness, short stature, and bone deformities are prevalent.
- Hearing loss: Hearing impairment is common, and can range from mild to severe.
- Cardiovascular problems: Heart valve defects and enlarged hearts can occur.
- Respiratory issues: Frequent respiratory infections and airway obstruction can be challenging.
- Hepatosplenomegaly: Enlarged liver and spleen are frequently observed.
- Skin problems: Skin thickening and corneal clouding can occur.
- Behavioral difficulties: Hyperactivity, aggression, and autistic-like behaviors can be present.
Causes
Hunter syndrome is caused by a deficiency of the iduronate-2-sulfatase enzyme, responsible for breaking down complex sugars called glycosaminoglycans (GAGs). Without this enzyme, GAGs accumulate in various body tissues, leading to the characteristic symptoms of the disorder.
Inheritance/recurrence risk
Hunter syndrome is an X-linked recessive disorder. This means that the defective gene is located on the X chromosome, and males are more likely to be affected. Females usually carry the gene but don‘t show symptoms, though they can pass it on to their sons. The chance of having a child with Hunter syndrome depends on the carrier status of both parents.
- If the mother is a carrier and the father is unaffected: There is a 50% chance their son will inherit the disorder and a 50% chance their daughter will be a carrier.
- If the father has Hunter syndrome and the mother is unaffected: All daughters will be carriers, and all sons will be unaffected.
