diagnosis and testing

Many of the early signs and symptoms of Hunter syndrome (MPS II) are commonly seen in unaffected infants and toddlers, so the road to diagnosis often takes time. As a parent or caregiver, it’s important to be an advocate for your child. Educating yourself and providing information to your pediatrician can go a long way toward getting a diagnosis more quickly.

It may take a while to get an appointment with a medical geneticist or genetic counselor, but don’t be discouraged. In order to confirm a Hunter syndrome diagnosis, various tests will need to be carried out and each of these will take time.

Diagnosis Doesn’t Have to be Rare

Young boy with Hunter syndrome.


Some states have initiated newborn screening for MPS II in an effort to identify the disorder at the earliest opportunity. The test is called blood spot screening, and consists of a few drops of blood being taken from the baby’s heel to measure I2S activity and GAG levels.

To learn more about newborn screening and find out if it is offered where you live, visit newbornscreening.hrsa.gov/conditions/ mucopolysaccharidosis-type-II.


Urinary glycosaminoglycan (GAG) testing provides a non-invasive, widely available means of screening for MPS disorders. For this test, a urine sample is analyzed to determine the level of GAGs. The presence of the specific GAGs dermatan sulfate and heparan sulfate in the urine could indicate Hunter syndrome. When clinical suspicion of MPS has been raised, additional laboratory testing is often necessary to confirm diagnosis of a specific MPS type.

Doctor performing a test for Hunter syndrome on a young male patient
Parent and child with Hunter syndrome holding a stuffed bear speaking to a doctor


To confirm a diagnosis of Hunter syndrome, the activity of iduronate-2- sulfatase (I2S) , the enzyme missing or deficient in Hunter syndrome, is measured. This can be done by taking blood and testing the I2S activity in serum or white blood cells, or by taking a skin biopsy and testing the I2S activity in skin fibroblasts.


If you have a child with Hunter syndrome or have a family history of this condition, prenatal diagnosis is available by measuring I2S enzymatic activity in amniotic fluid or in chorionic villus (placental) tissue. Prenatal diagnosis is also available via mutation analysis.

Caregiver reassuring pregnant mother


In order to identify female carriers (who are not affected by Hunter syndrome but carry the affected gene) of the disease, it is necessary to identify the mutation of the I2S gene using mutation analysis. This can provide the geneticist with information that can help them to assist with family planning decisions.