What is MPS 7?

Mucopolysaccharidosis type 7 (MPS 7) is an inherited metabolic disorder. Like other types of MPS disease, MPS 7 is caused by an enzyme deficiency in the processing of glycosaminoglycans (GAGs). In MPS 7, patients lack the enzyme, beta-glucuronidase, which is required for the degradation of the GAGs dermatan sulfate (DS), heparan sulfate (HS), and chondroitin 6 sulfate (CS). 

MPS 7 is also called Sly Syndrome, as it was first described by Dr. William Sly in 1973. It is an extremely rare form of MPS.

Patients with MPS 7 may experience joint stiffness, short stature, an enlarged spleen and liver and heart / lung complications. MPS 7 also causes a characteristic facial appearance and can lead to a progressive skeletal dysplasia. Hearing loss, cataracts and clouding of the corneas are also symptoms of patients with MPS 7. In more severe cases, there may be developmental delay. The severe form of MPS 7 can uniquely present at birth with hydrops fetalis (severe generalized edema). This is a very severe neonatal condition in which the child retains an enormous amount of fluid throughout the body. More than half of infants with hydrops fetalis do not survive beyond early infancy. Some adults with MPS 7 can have a less severe physical or skeletal disease.


There are no approved specific treatments for MPS 7.

Recent results from a long-term Phase 1/2 study determined the optimal dose of the investigational enzyme replacement therapy (rhGUS; UX003) along with other supportive data. These data showed that among the three dose levels tested, the 4 mg/kg dose of rhGUS led to the greatest reduction of glycosaminoglycans (GAGs) in the urine, with an average reduction of GAGs in the urine of approximately 60%. In two people who had enlarged livers at the start of the study, there was a decrease in liver size. There was an improvement in pulmonary (lung) function observed in the one patient who was able to perform the evaluations. No serious adverse events or treatment-related infusion-associated reactions related to the investigational enzyme therapy were reported in the study after 36 weeks of treatment. The most common adverse events were consistent with symptoms of MPS 7 and were respiratory disorders, infections, joint pain, and infusion site extravasation.

Patient Support

International MPS Network

Country organizations include:

Hong Kong
New Zealand
US National MPS Society

If you are a member of an MPS patient organization and would like to be listed here, please contact us.

Current Activities

Ultragenyx is studying rhGUS, an investigational product, intended for the treatment of MPS 7. 

Ultragenyx is sponsoring a Phase 3 study of rhGUS in people with MPS 7. For more information about the study, please visit the study page.

A study of rhGUS in children with MPS 7 under 5 years of age is ongoing.  For more information about this study, please visit the study page.

A Phase 1/2 study is ongoing in people with MPS 7, but not currently recruiting. For more information about this study, please visit the study page.

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