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Genome sequencing used to diagnose boy's rare disease

July 22, 2011 12:00:00 AM PDT
A decade after the human genome project created the first complete blueprint of a human being, a young boy with a rare, devastating disease is one of the first to benefit from that effort.

Like most kids his age, Nic Volker loves playing with his cars and asking, "Why?"

But he's far from your typical 6-year-old. He's a medical mystery, spending more than 700 days in the hospital with a gut disease doctors couldn't diagnose.

"What the surgeon would tell me is that, 'We're just keeping him alive,'" recalled Nic's mom, Amylynne Santiago Volker.

Nic's journey began shortly before his second birthday. Doctors thought he might have Crohn's disease. He wasn't eating and dropped down to 17 pounds.

"He couldn't walk anymore and he was always in pain," said Amylynne Santiago Volker.

It got worse and a temporary colostomy provided little relief. Nic developed a blood infection, called sepsis, and was given three days to live. At one point, he had so many ulcers in his stomach, holes began to appear all over his abdomen and stool began spilling out.

"I didn't want him to die. He was so sick and he wasn't healing and I wanted to, you know, I wanted someone to find the answers for him," said Amylynne Santiago Volker.

Believing his genes could hold the key, doctors at Children's Hospital of Wisconsin/Medical College of Wisconsin decided to do something that had never been done before -- sequence Nic's genome and base his future treatments on their findings.

"Nic was the first case in the world that I think anyone is aware of where genome-wide or exome-wide sequencing was used to make a diagnosis," said Dr. David Dimmock, MD, assistant professor of pediatric genetics at Medical College of Wisconsin.

After looking at 20,000 genes, doctors pinpointed the mutation responsible for Nic's illness: XIAP deficiency. Dr. David Margolis, professor of pediatrics at Medical College of Wisconsin, described it as Nic's immune system missing a protein.

The diagnosis meant doctors could treat Nic with a bone marrow transplant using umbilical cord blood -- essentially giving him a new immune system. Now, Nic's back to playing and, more importantly, eating.


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