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New clinic seeks clues to rare childhood genetic disorder

Feb. 26, 2014, 11:00 AM

Taking part in the first Alternating Hemiplegia of Childhood (AHC) clinic were, from left, Cate Cohen and her son, Asher, Mollie Erpenbeck and her son, Austin, and Candice Peay and her daughter, Cassidy. (photo by Anne Rayner)

A new specialty clinic at the Monroe Carell Jr. Children’s Hospital at Vanderbilt is dedicated to investigating and treating a rare childhood disorder that causes partial — and sometimes nearly total — paralysis for unpredictable lengths of time.

The genetic disorder, Alternating Hemiplegia of Childhood (AHC), typically begins before 18 months of age and causes a host of challenges, including sporadic paralysis affecting either side of the body, seizures, debilitating muscle contractions, abnormal eye movement, difficulty walking and developmental delays.

The AHC clinic at Children’s Hospital is led by Kevin C. Ess, M.D., Ph.D., director of the Division of Pediatric Neurology. The clinic arose out of an AHC research collaboration by Ess and Alfred George Jr., M.D., director of the Division of Genetic Medicine.

Their research project was made possible thanks to a grant from the Alternating Hemiplegia of Childhood Foundation (AHCF).

AHC is exceedingly rare, and has been diagnosed in approximately 1,000 children worldwide. The causative gene, ATP1A3 was only recently discovered, so that number is expected to rise as knowledge of the disorder grows.

Kevin C. Ess, M.D., Ph.D.

“The genetics are just now getting worked out, so there likely will be many more diagnosed,” Ess said. “It’s very rare and relatively recently discovered, and at this time, really, the parents have been the de facto experts.

“We’re excited about the genetic research we’ll be able to do and the possible therapies we’ll explore. Through our research, we’re hopefully going to identify new therapies and medications that may help alleviate the symptoms of AHC,” Ess said.

Three families of children with AHC recently traveled to Children’s Hospital from Kentucky and Ohio to take part in the first session of the new clinic and to celebrate its creation.

All of them know firsthand the toll AHC takes on children and families.

Cate Cohen’s son, Asher, 6, is on the milder end of the AHC spectrum. Most of his episodes, which take place every eight days or so, involve paralysis of one of his arms. Sometimes both the arm and leg are affected.

There are also times when he is paralyzed from the neck down.

“With Asher, full body paralysis is about 5-10 percent of the time, and those are painful,” Cohen said. “In general, with AHC kids, episodes can last an hour, a day or five days. But we’re fortunate with Asher, because severe, painful paralysis isn’t as frequent as it can be for others. There are families out there who have painful episodes every few days.

“It’s different for every child; some suffer with episodes every day, others every week and still others a few times a month.”

Sean Donahue, M.D., conducts an impromptu eye exam on Cassidy Peay during a recent lunch to celebrate the debut of a new specialty clinic dedicated to Alternating Hemiplegia of Childhood (AHC). (photo by Anne Rayner)

When he was younger, Mollie Erpenbeck knew a key sign that her son, Austin, 4, was about to suffer an episode was when his eye movements would begin to deviate.

Those eye movements brought the Erpenbecks to Vanderbilt to see Sean Donahue, M.D., Ph.D., Sam and Darthea Coleman Professor of Pediatric Ophthalmology, who made the diagnosis of AHC when Austin was 5 months old.

“Now Austin tells me when he feels them coming on. Every other week he has paralysis of part of his body for up to a week. The longest was 14 days full-body,” Erpenbeck said.

Candice Peay brought her daughter, Cassidy, 2, and son, Zayne, 10, to the clinic’s debut. Peay never knows when Cassidy’s episodes will happen or how long they will last, but she knows it takes the entire family to cope with the disorder.

“It can be hard on the whole family. The other children have to learn how to sacrifice when she’s in an episode,” Peay said. “You really have to have a plan, and a backup plan.”

Part of that plan now includes the new AHC clinic at Vanderbilt, which will investigate potential new treatment drugs and conduct genetic testing as needed for mutations in the ATP1A3 gene.

“As parents of children with AHC we are thrilled that Vanderbilt has jumped on board and is helping to lead the way in fighting this disease,” Cohen said.

“It really is a blessing because they are working to change the course of these children’s lives.”

To learn more about the Alternating Hemiplegia of Childhood Foundation, go here.

To learn more about the AHC clinic at Vanderbilt, go here.

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