Creutzfeldt-Jakob Disease (CJD)
What Is It?
Creutzfeldt-Jakob disease (CJD) is a rare, fatal brain disorder caused by prions. Prions are normal proteins that have changed their shape. Healthy proteins have a healthy shape, which allows them to function normally. The misshapen prion protein causes disease by making other proteins nearby change their healthy shape to the prion's unhealthy shape. In this way one prion makes many more prions: it slowly turns healthy proteins into prions, too.
When symptoms eventually appear, CJD causes rapidly progressive dementia (mental decline) and involuntary jerking muscle movements called myoclonus. About 90% of people with CJD die within 1 year of diagnosis.