Think of it this way: when your garbage can gets full, you take out the trash. But what if you can’t? What if bag after bag fills up, taking over your kitchen? Soon, it would be hard to walk around, cook, or clean. As the trash builds even higher, your kitchen becomes unusable. Similarly, children with Mucopolysaccharidosis Type II (MPS II), also known as Hunter syndrome, are unable to make the enzyme that takes care of our cellular garbage; their bodies becoming like the kitchen in this example.
How Do You Recognize Hunter Syndrome?
Hunter syndrome is a rare genetic disease that is progressively debilitating, life-limiting and without a cure. It occurs almost exclusively in males and currently affects approximately 500 boys in the U.S. and less than 2,000 worldwide. Individuals with Hunter syndrome have a defect in the gene that normally causes the body to make the enzyme iduronate-2-sulfatase (I2S) – the “garbage man” – which is responsible for the breakdown of cellular waste called glycosaminoglycans or GAGs – the cell’s “garbage.” Without that necessary enzyme, the accumulation of these GAGs leads to progressive damage throughout the entire body.
Though the disease is present at birth, symptoms become more apparent as the accumulation of GAGs builds within the body, triggering a diagnosis usually between 2 to 4 years old. Most boys with Hunter syndrome continue to develop physically and cognitively until between the ages 2 and 5 and then begin regressing. These boys gradually lose the ability to talk, walk and eat. Most do not live to see their teen years. Approximately 20% of those affected by Hunter Syndrome do not suffer cognitive impairments or regression and may have normal intelligence but a continuum of physical symptoms.
Can Hunter Syndrome Be Cured?
No cure exists for Hunter syndrome. Currently, the only FDA-approved treatment on the market, enzyme replacement therapy (ERT), can stabilize many of the physical symptoms of Hunter syndrome. However, as it cannot cross the blood-brain barrier, it is unable to prevent cognitive regression, meaning the child will continue to decline to an infantile state.
How Common Is Hunter Syndrome?
Hunter syndrome (Mucopolysaccharidosis/MPS II) is a rare condition affecting between 1 in 100,000 to 1 in 150,000 male births, although it is estimated that the grouping of MPS conditions collectively affect 1 in 25,000 births in the United States (MPS conditions include MPS I, II, III, IV, VI, VII and ML II and III).