Decoding the Mysteries of Mucopolysaccharidosis Type II: Understanding, Diagnosing, and Genetic Testing

Expert Reviewed By: ⁠Dr. Brandon Colby MD

Understanding Mucopolysaccharidosis Type II

Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome, is a rare genetic disorder that affects the body’s ability to break down complex sugar molecules called glycosaminoglycans (GAGs). When GAGs accumulate in the body, they cause progressive damage to various organs and tissues, leading to a wide range of symptoms. The severity of MPS II can vary, with the mild form of the disease allowing for a longer life expectancy and a slower progression of symptoms compared to the severe form.

Diagnosing Mucopolysaccharidosis Type II

Diagnosing MPS II can be challenging due to the variability of symptoms and their resemblance to other conditions. However, a combination of clinical findings, enzyme assays, and genetic testing can help confirm the diagnosis. Enzyme assays measure the activity of the enzyme iduronate-2-sulfatase (I2S), which is deficient in individuals with MPS II. A low level of I2S activity is indicative of the disorder. Genetic testing can then be used to identify disease-associated variants in the IDS gene, which provides further evidence for the diagnosis of MPS II (source).

Genetic Testing for Mucopolysaccharidosis Type II

Genetic testing plays a crucial role in the diagnosis and management of MPS II. It can be used to identify disease-associated variants in the IDS gene, which is responsible for producing the I2S enzyme. Identifying these variants can help confirm the diagnosis of MPS II and provide valuable information about the severity and progression of the disease.

Uses of Genetic Testing: Prenatal Diagnosis

For families with a history of MPS II, genetic testing can be performed during pregnancy to determine if the unborn child is affected by the disorder. Prenatal diagnosis can be achieved through chorionic villus sampling (CVS) or amniocentesis, which involve collecting samples of placental tissue or amniotic fluid, respectively. These samples can then be analyzed for the presence of disease-associated variants in the IDS gene (source).

Uses of Genetic Testing: Carrier Testing

Carrier testing can be performed on individuals who have a family history of MPS II but do not show symptoms of the disorder. This type of genetic testing can help identify if a person carries one copy of the mutated IDS gene, making them a carrier of the disease. If both parents are carriers, there is a 25% chance that their child will inherit two copies of the mutated gene and develop MPS II.

Uses of Genetic Testing: Newborn Screening

Although newborn screening for MPS II is not yet universally implemented, it has the potential to significantly improve early diagnosis and treatment outcomes for affected individuals. Early identification of MPS II through newborn screening can allow for prompt initiation of treatment, such as enzyme replacement therapy, which has been shown to slow the progression of the disease and improve the quality of life for patients with mild forms of MPS II (source).

Conclusion

Mucopolysaccharidosis type II is a rare genetic disorder with a wide range of symptoms and varying degrees of severity. Genetic testing plays a crucial role in diagnosing MPS II and can provide valuable information about the severity and progression of the disease. Additionally, genetic testing can be used for prenatal diagnosis, carrier testing, and newborn screening, allowing for early identification and treatment of the disorder. As research continues to advance, it is essential to raise awareness about MPS II and the importance of genetic testing in managing this rare condition.

About The Expert Reviewer

Dr. Brandon Colby MD is a US physician specializing in the personalized prevention of disease through the use of genomic technologies. He’s an expert in genetic testing, genetic analysis, and precision medicine. Dr. Colby is also the Founder of  and the author of ⁠⁠Outsmart Your Genes.

Dr. Colby holds an MD from the Mount Sinai School of Medicine, an MBA from Stanford University’s Graduate School of Business, and a degree in Genetics with Honors from the University of Michigan. He is an Affiliate Specialist of the American College of Medical Genetics and Genomics (⁠⁠ACMG), an Associate of the American College of Preventive Medicine (⁠⁠ACPM), and a member of the National Society of Genetic Counselors (⁠NSGC)