Most people with a rare type of dementia called primary progressive aphasia (PPA) have a specific combination of prion gene variants, a new study shows. The study is the first to link the prion protein gene to this disorder. It was funded in part by the National Institute of Neurological Disorders and Stroke (NINDS), part of the National Institutes of Health (NIH), and appears in the December 2005 issue of the Annals of Neurology.
The researchers, led by James A. Mastrianni, M.D., Ph.D., of the University of Chicago, also looked at the prion protein gene in people with Alzheimer's disease and amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease) and did not find any association with specific gene variants in those disorders.
PPA is classified as a type of frontotemporal dementia because of the pattern of brain degeneration it causes. The primary symptoms of the disease are problems speaking or understanding speech, and these problems gradually get worse over time. People with PPA also may develop difficulty with math. Most other functions remain normal for at least two years after the language symptoms appear, but the disease may eventually cause other changes, such as problems with memory, reasoning, and spatial abilities. While PPA sometimes runs in families, it has never before been linked to variations in a specific gene.
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