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 is unhealthy. Worse, the prion causes disease by making other proteins nearby change their healthy shape to the prion's unhealthy shape. In this way a prion makes 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.
About 85-95% of cases of CJD are from sporadic mutations. The DNA in a brain cell is changed by the mutation, and makes an unhealthy prion protein. Less often, the mutation is hereditary (passed down from parent to child). Jewish people born in Czechoslovakia, Chile and Libya have a higher-than-average number of inherited cases of CJD. Inherited CJD does not cause symptoms until adulthood.