Creutzfeldt-Jakob Disease (pronounced KROITS-felt/YAH-kohb) was diagnosed independently in the early 1920s by the two men after whom the disease was named. However, as noted earlier, the cause wasn’t understood until the late 1990s with the discovery of prions. Basically there are three types of classic prion diseases, or CJD: sporadic, familial, or inherited (although it might be debated whether sporadic and iatrogenic forms should be included in infectious prions). However, since the source of the disease is either unknown or accidental, they are categorized as classic CJDs. Sporadic CJD accounts for between 85-90% of diagnosed classic CJD cases. It is estimated that one person per million people develops the disease. Familial or inherited CJD accounts for about 10-15% of the diagnosed cases while iatrogenic CJD accounts for less than one percent of the diagnosed cases. One of the reasons that classic CJD is difficult to diagnose is because, in the early stages, the symptoms often mimic those of Alzheimer's Disease, Huntington's Disease, or Parkinson's Disease. Early symptoms for both the sporadic and iatrogenic CJD include mood swings, anxiety, memory lapses, anti-social behavior such as noticeable withdrawal, lapses in memory, a lack of coordination, and insomnia. As the disease progresses, patients generally experience marked deterioration in their vision, dementia, involuntary muscle contractions that develop into muscle paralysis, a slurring of speech, difficulty in swallowing, incontinence, and eventually coma.