Adult onset that isn't linked to a genetic event is even more uncommon, Dr. Holter says.

CNN: iReport: 'Billy's Disease' baffles doctors

Today, the cardiologist said, she would get a stress test, an echocardiogram, a mobile Holter monitor, and maybe even a cardiac catheterization.

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Cheney was wearing a harness device, known as a Holter ECG monitor, and the four episodes were detected over 34 hours, Glover Weiss said.

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Dr. Jennifer Holter, who has been treating Billy at Oklahoma University Medical Center since the fall of 2008, says several immunologists have reviewed his case but the underlying reason for his immunodeficiency is still unclear.

CNN: iReport: 'Billy's Disease' baffles doctors