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CHOC Pioneers Combination Treatment for Inherited Disease

Last October, 11-month-old Sawyer Leestma, of Huntington Beach, became the first child in the country to be treated with a combination of Aldurazyme™ enzyme replacement therapy and bone marrow transplantation for Mucopolysaccharidosis 1 (MPS 1). By undergoing the newly approved enzyme replacement therapy first, Sawyer was healthier and stronger, and more able to resist the rigors of a bone marrow transplant.

One year later, the bone marrow transplant has been a complete success. Sawyer has been off all medications since June and appears to be completely cured of MPS 1.

CHOC pediatric metabolic specialist Jose Abdenur, M.D., who coordinates Sawyer’s care with a diverse team of CHOC specialists, has presented Sawyer’s case to various medical societies, including the 2004 annual meeting of the Society of Inherited Metabolic Diseases. His results will soon be published in a collaborative study involving 11 additional patients who have subsequently undergone combination therapy for MPS 1 at other facilities around the country.

Our physicians don’t use words like “cure” or “medical breakthrough” lightly, but they are very excited about a new therapeutic strategy that is quickly becoming the standard of care for a rare, debilitating and potentially deadly inherited disease. Last October, CHOC became the first hospital to use enzyme replacement therapy in combination with bone marrow transplantation to treat Mucopolysaccharidosis 1 (MPS 1). Months before his bone marrow transplant, Sawyer Leestma began receiving weekly infusions of Aldurazyme™ enzyme replacement therapy, a brand-new form of treatment for MPS 1 that had been approved by the FDA only a few months previously.

Aldurazyme™ dramatically improved Sawyer’s overall physical condition, making him stronger and better able to withstand the rigors of bone marrow transplantation. In October, Sawyer, then 11 months old, received new bone marrow from a closely matched donor. He continued with the weekly Aldurazyme™ treatments through mid-December, until the new bone marrow engrafted and his own body started producing the formerly missing enzyme. Now a year out from transplant, Sawyer appears to be completely cured of MPS 1, and has been off all medications since June.

Sawyer’s case clearly showed how Aldurazyme™ halts the progression of, and in some cases actually reverses, the physical effects caused by MPS 1, and how it helps patients prepare for bone marrow transplantation. Furthermore, it is a break-through treatment alternative in situations where bone marrow transplantation is not an option.


Mucopolysaccharidosis 1 (MPS 1) is an inherited metabolic disorder of varying severity formerly referred to as Hurler, Scheie or Hurler/Scheie Syndrome. Children with MPS 1 lack the necessary enzyme to breakdown mucopolysaccharides, the long chains of sugar molecules used in connective tissue throughout the body. Without this enzyme, the mucopolysaccharides cannot be removed from the cells. Instead, they build up in the cells, causing progressive damage. “All children with MPS 1 lack the same enzyme, but the severity of each case varies. Some children suffer neurological damage and die before age 10. Others may have normal or near-normal intelligence and live into adulthood,” says pediatric metabolic specialist Jose Abdenur, M.D., medical director of CHOC Metabolic Services. “At this time, there is no accurate way of predicting how far the condition will progress without treatment.”

And that is the difficult part in treatment planning. Aldurazyme™ cannot reverse or halt the progression of neurological damage because it does not reach the brain. Only bone marrow transplantation, a risky procedure in itself, prevents the neurological damage that may be caused by MPS 1.

“The major challenge is predicting whether a child with MPS 1 will suffer neurological impact from this disease. Some never do,” Dr. Abdenur says. “The question is whether to continue with weekly enzyme replacement hoping the patient will never have neurological problems, or to combine it with bone marrow transplantation, which also targets the brain.”

Those were the choices facing Michele and Charles Leestma. After researching their options, they decided to try a combination of both treatment strategies with their son, Sawyer. A year later, the Leestmas have no doubt they made the right choice.

“We opted for bone marrow transplantation in addition to enzyme therapy because we were concerned about Sawyer’s neurological development,” Michele says. “Some patients who had bone marrow transplants 20 years ago for MPS 1 are living normal lives. Without one, Sawyer might not have lived past the age of 10.”


Christian Munoz, 5, and his little brother Ryan, 1, also have MPS 1. They spend every Wednesday at CHOC, from 8 a.m. to 3 p.m., undergoing Aldurazyme™ enzyme replacement therapy. They also receive frequent evaluations from several CHOC specialists in addition to Dr. Abdenur, including hematologists, ENTs, cardiologists, surgeons, radiologists, psychologists, ophthalmologists, orthopedists, pulmonologists and rehabilitation therapists.

Right now, Christian and Ryan have some of the physical abnormalities associated with MPS 1, but none of the neurological damage that is usually seen during the first two years of life. Still, should a bone marrow transplant become necessary, their 2-year-old brother, Tyler, is a perfect match for both of them.

“We are following Christian and Ryan extremely closely with MRIs and neurodevelopmental assessments every six months,” Dr. Abdenur says. “They are also undergoing physical, occupational and speech therapy, so we can detect any neurological abnormality very early. If anything develops, we are fully prepared to go ahead with a bone marrow transplant.”


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Children's Hospital of Orange County is affiliated with UC Irvine Healthcare and UC Irvine School of Medicine

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