November 7, 2008

Novel transplant eases infant’s rare genetic disorder

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Stephanie Hamilton holds her infant son, Destin, who was treated at Vanderbilt for an extremely rare genetic disorder causing high levels of ammonia that often lead to brain damage or death. (photo by Susan Urmy)

Novel transplant eases infant’s rare genetic disorder

Within hours of taking his first breath on Aug. 1, unknown to everyone around him, Destin Hamilton was getting sicker by the minute.

The newborn had a genetic defect creating a dangerously high ammonia level that typically leads to brain damage and often death.

Luckily for Destin, his doctors in Bristol, Tenn., recalled a lecture given by a group of Vanderbilt Medical Center geneticists about carbamyl phosphate synthetase deficiency (CPS-1), a urea cycle disorder.

Seen in only one in 1 million births, the disorder is a defect in the first enzyme of the urea cycle that causes a person to be unable to process waste nitrogen.

Brendan Lanpher, M.D., assistant professor of Medical Genetics and Pediatrics was on service the day the call came in and coordinated Destin's transfer to the Monroe Carell Jr Children's Hospital at Vanderbilt.

Time was not on their side.

“The thing about high ammonia levels is that it causes brain damage and you have a small window of opportunity to reverse it and prevent permanent damage,” said Lanpher.

“This is a really tough disorder to diagnose. The classic patient presenting with elevated ammonia levels will go into a coma and be unresponsive, just as Destin did.

“But what that looks like to most people is a newborn with an overwhelming infection. The reaction is the same, said Lanpher, who credits William Devoe, M.D., of Johnson City Medical Center, with the difficult catch.

Destin's initial ammonia level was 591. Normal is less than 100. This testing is not a part of the newborn screening process.

Brought by LifeFlight to Vanderbilt, Destin was immediately placed on ECMO (extracorporeal membrane oxygenation). An ECMO machine is similar to a heart-lung bypass machine to take the place of an ineffective heart or lungs (or both), until medical treatments can restore the organ's function. In Destin's case, the ECMO machine allowed rapid dialysis to remove the toxic ammonia.

Once stabilized, the infant's care team faced an additional challenge. In order to save his life, he would need a liver transplant. Vanderbilt had never performed a liver transplant on a child so young or small. At birth Destin weighed 7.4 pounds. The goal — get Destin stronger and bigger.

“His story is quite remarkable,” said Lanpher. “He spent two months in the hospital while waiting for a transplant with no high ammonia levels.”

The infant's dietician, Gina Wey, was responsible for developing a formula specific to Destin's daily needs. Too much or too little protein in his diet would elevate the ammonia. It was critical that his levels be maintained while waiting on a liver.

It worked.

Destin weighed nearly 12 pounds when a compatible organ became available.

The life-saving transplant was performed on Oct. 1, which happened to be the one-year anniversary of Vanderbilt's Pediatric Liver Transplant Program.

“We were fortunate to receive a whole organ gift of donation,” said Beau Kelly, M.D., surgical director for the program.

“He is an absolutely remarkable child with all the right stars aligned behind him. He was diagnosed with a rare condition that most children either die from or sustain a profound neurological impairment. But he was diagnosed in such a fashion that he was immediately sent here, avoiding many of the issues these children develop.

“This exemplifies a coordinated and well-executed effort among our multi-disciplinary team,” Kelly said. “Liver transplant can be difficult, and in a patient less than 1 year old, it can be even more perilous. Then with this type of disease, receiving a transplant and maintaining an intact neurological outcome is unheard of.”

Destin is one of only five pediatric patients in the United States transplanted as a treatment for CPS-1.

Soon after being transplanted, Destin required an additional procedure to restore artery flow to his transplanted liver. Considered a substantial strike against him, he came through with no complications.

Stephanie Hamilton, Destin's mother, is still in awe of the medical intervention her son received.

“All I kept hearing was that his condition was fatal,” said Hamilton, 19. “It was just so much to take in. I wanted to give him a portion of my liver. But even a part of mine would have been too big, plus I was the primary caregiver so it was not an option.

“It was just so hard. I didn't know how to help him. I was so scared and nervous. This is not what you expect when you have your first child…everything is supposed to be perfect.”

Now 3 months old, Destin is expected to be discharged from Vanderbilt to an area hotel. His medical team will continue to monitor him and in the next week he'll head back home to Bristol.

“Instead of asking how much my child weighs or how long he is, my biggest questions will focus on his labs and medication schedule, and I'm OK with that,” said Hamilton.

“This is such a great hospital,” she said, smiling. “It's not the experience I wanted, but what Destin has faced will help someone else. He's healthy, and not everyone can say that.”