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Root of the Issue

Scripps scientists have been able to shed light on the cause of seizures and other problems that have been plaguing 10-year-old Calista Mellos since birth, U-T San Diego reports.

As part of the IDIOM — the Idiopathic Diseases of Man — study, the Scripps team has been using whole-genome sequencing to try to understand otherwise cryptic diseases. As Jennifer Kearney and her colleagues report in the Annals of Neurology, they sequenced the Calista, her parents, and her sister to find that the girl has a de novo missense mutation in the KCNB1 gene, which encodes a voltage-gated potassium channel. Functional studies, the researchers add, indicate that mutations affecting the channel can lead to a loss of ion selectivity and to depolarizing inward cation conductance.

Based on these findings, Calista's doctors adjusted her care to include more potassium and to keep her better hydrated, especially in the summer, U-T San Diego's Bradley Fikes says. This, Fikes adds, has helped some of her attacks, though she still does have some seizures.

"She began having periods that could last several hours when she was a perfectly normal child and you wouldn't know a thing was wrong with her," her pediatrician Robert Bjork tells him. "She has a sense of humor and is much more capable in a lot of areas."

Still, Fikes notes that Calista has been lucky. Fifteen patients have been sequenced thus far as part of the IDIOM study and mutations have been found in 10 patients, but only three patients, including Calista, have received a definitive diagnosis.