One Enzyme Short: How a Clinical Trial Made All the Difference for a Young Boy with a Metabolic Disease

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Sutton Piper, age 3

Sutton Piper, 3, was born with a metabolic disorder that made his muscles too weak for crawling, walking and talking. After being referred to Dr. Sihoun Hahn, a biochemical geneticist at Seattle Children’s, Sutton is bouncing on his mini-trampoline and chatting up a storm. 

Sutton Piper came into the world on his own terms: nine days late.

At 6 months, he’d made little attempt at rolling over; at 9 months, he showed no interest in sitting up on his own; and, by his first birthday, he wasn’t even trying to crawl.

“We kept thinking he was just a late bloomer,” remembers Kelly Piper, Sutton’s mom. “We’d read about babies who skip crawling and go right to walking. We tried not to worry by telling each other he was one of those kids who would meet all the developmental milestones in his own sweet time.”

Once Piper weaned Sutton from breast milk, he stopped wanting to eat and started losing weight. She and her husband Mike, who live in the small eastern Washington town of Otis Orchards, took their son to a neurologist. When the doctor suggested a brain scan, the couple knew something was terribly wrong. Though the results came back normal, a tissue sample revealed he probably had Pompe disease — a genetic metabolic disorder.

Later the Pipers learned they are both carriers of the disease. Together, they have a 50% chance of having a child who is a carrier and a 25% chance each of producing a child with or without Pompe. Sutton’s older brother Landon, now 7, is not affected, but only a future DNA test will reveal if he is a carrier.

For Sutton, the disease meant he was missing a critical enzyme that helps cells break down the fuel needed to power muscles. It was the accumulation of this undigested fuel in his muscle tissue — and not a slowpoke nature — that made him too weak to do much of anything.

Looking for the needle in the haystack


Dr. Sihoun Hahn
Dr. Sihoun Hahn

When Dr. Sihoun Hahn started his pediatrics career as a biochemical geneticist nearly 30 years ago, he says he was naïve. “I assumed much more was known about how the body breaks down proteins, fats and carbohydrates — and why inherited metabolic disorders happen. I came to learn we knew very little.”

So Hahn worked to make significant contributions to the field. He’s spent his career identifying defects in single genes that wreak havoc on the body’s ability to convert food to energy. He’s also developed powerful tests (called assays) to diagnose the most common and treatable of these disorders. (There are hundreds of different genetic metabolic disorders, and their symptoms, treatments and prognoses vary widely.)

Today, as director of Seattle Children’s Biochemical Genetics Program and a scientist in Seattle Children’s Center for Developmental Therapeutics , Hahn leads one of the largest teams in the nation that detects, diagnoses and treats metabolic disorders — and the only one in the region. Clinicians in the program­, including geneticists, genetics counselors, metabolic nutritionists, nurse practitioner, nurse and a social worker, follow more than 1,500 patients from infancy through adulthood because patients with metabolic diseases must receive medical care for their entire lives.

Since arriving in Seattle eight years ago, Hahn has also worked closely with the state of Washington to increase the number of metabolic disorders on the state’s newborn screening panel from five to 20. In 2013, the state referred 66 cases of possible metabolic disorders to Seattle Children’s Genetics Laboratories for confirmation. Of those cases, 25 were positive.

“Early diagnosis prevented the mental and physical impairment of these infants,” says Hahn. “It also significantly reduced future medical costs associated with their conditions.”

Research brings hope

Sutton was lucky. He was born with a mild form of Pompe. Though his condition went undiagnosed in infancy (Washington state does not yet screen newborns for the disease), he survived until the age of 20 months when his neurologist referred him to Seattle Children’s.

Kelly and Mike Piper (Sutton's parents), Sutton Piper (left) and his brother Landon Piper (right)
Kelly and Mike Piper (Sutton’s parents), Sutton Piper (left) and his brother Landon Piper (right)

Hahn ran enzyme and DNA assays to confirm Sutton’s condition and enrolled him in a clinical research study offered at Seattle Children’s for a new enzyme replacement medication called Lumizyme.

Sutton received his first biweekly dose of the experimental drug in January 2013. Less than five months later, at the age of 27 months, he started walking.

“Words can’t express what Dr. Hahn’s study meant for our family,” says Piper. “We feared the worst for Sutton and now he’s able to climb stairs and stand up from sitting on the floor.”

In August 2014, the FDA approved Lumizyme as a safe and effective treatment for pediatric Pompe disease. Sutton continues to grow stronger with the new enzyme replacement therapy (he refers to his infusions as “getting his muscle juice”) and Hahn continues his research to improve the way we detect, diagnose and treat metabolic disorders.

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  • Washington State Department of Health Office of Newborn Screening