MPS I (or mucopolysaccharidosis I) is so rare, most doctors will never see a single case of this progressive and potentially fatal inherited disease in their lifetimes. It affects just one out of 100,000 Canadians.

Its wide range of symptoms, which can vary widely, includes recurrent respiratory infections and stiff joints, to enlarged spleen and liver, making diagnosis challenging for physicians.

For doctors like Dr. Aneal Khan, from the department of medical genetics at Alberta Children’s Hospital in Calgary and an associate professor, increasing awareness of this type of rare disease among physicians is crucial for getting patients diagnoses and treatment sooner.

Greater awareness needed for rare genetic diseases

“I think one of the key things is, with any really rare disease, is to try to bring the perspective that there are many such rare diseases,” says Dr. Khan. “Their overall impact, particularly in children, is quite significant. If you look at the number of hospitalizations and number of sick days that children have from rare diseases, it’s not small. MPS I is one of hundreds of rare diseases — one that there are effective treatments for. Therefore, they need to be on the radar.”

Often times, infants with MPS I may appear normal at birth, but signs of the disease appear within two years. Parents may notice, for example, that they aren’t growing as quickly as other children of the same age, or there’s a kind of swelling of the facial features, clouding of the cornea, or even a delay in speech and impaired hearing.

Those are some of the common things physicians may encounter that may prompt further investigation. It may lead to diagnosing the severe form of the disease called Hurler Syndrome, usually present in infants under the age of one.

At the other end of the spectrum, there’s a mild form called Scheie Syndrome that might affect adults. Many may not know they have the disease until a medical issue prompts a visit to a physician. In between the severe cases of MPS I in children and the milder form in adults is another intermediate type called Hurler-Scheie.

Advanced research determines MPS I cause and treatments

MPS I is not a contemporary disease. In 1919, Dr. Gertrude Hurler, a German pediatrician, first described the condition upon examining two child patients.

The milder form of the disease was named in 1962 by American ophthalmologist Dr. Harold Scheie. Since then, researchers have been able to pinpoint a cause. It’s an inherited disease resulting from a defective gene responsible for the production of the enzyme alpha-L-iduronidase.

That means long chains of complex sugar molecules called glycosaminoglycans (GAGs) used in the building of bones, cartilage, skin, tendons, and many other tissues can’t be broken down. Instead these GAGs build up in cells, eventually leading to cell, tissue, and organ damage.

“Now, with genetics being such a big part of medicine, it's getting easier to identify many of these diseases,” says Dr. Khan. “We sometimes think of them as new diseases, but they've probably been around for a long time.”

In those affected with a severe form of the disease, it’s important to diagnose cases early. As Dr. Khan points out: “Most children that present after a year of age may not make it until their 10th birthday, unfortunately. There is a treatment, though, that can change that.”

Managing a rare disease with transplants

While there is no cure for MPS I, it can be managed using a hematopoietic stem cell transplant (HSCT), also known as a bone marrow transplant, before the onset of neurologic disease and certain changes in the brain. Generally under two years of age, the outcome is better than transplanting them later, or with severe neurologic disease. That underscores the importance of an early diagnosis.

Another option for patients with the milder forms of MPS I is enzyme replacement therapy. Studies have shown that treatment for 26 weeks helps to improve lung capacity, while shrinking the liver. Though there have been recent advances in treatment for the disease, it remains largely under the radar.

“I don't expect most physicians to tuck away what MPS I is in their minds,” says Dr. Khan. “Unfortunately, I want them to tuck [away] that if a child comes in with growth problems, enlarged organs, problems with their skeleton, something unusual, that there are specialists that can try to find out whether this is one of those rare genetic diseases.”