Creutzfeldt-Jacob disease is caused by –
**Core Concept**
Creutzfeldt-Jacob disease (CJD) is a rare, degenerative, fatal brain disorder caused by an infectious agent that affects the brain's normal functioning. It is a type of prion disease, characterized by the accumulation of abnormally folded prion protein in the brain, leading to neuronal damage and death.
**Why the Correct Answer is Right**
The correct answer is a prion, specifically the prion protein (PrP^Sc), which is an abnormally folded version of the normal cellular prion protein (PrP^C). The disease is caused by the transmission of this abnormal prion protein from an infected individual or contaminated tissue. Prions are unique in that they are infectious proteins that can induce normal proteins to misfold into the disease-causing form. This process leads to the formation of amyloid plaques and neuronal loss in the brain, resulting in the characteristic symptoms of CJD, such as dementia, memory loss, and difficulty with coordination and movement.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because CJD is not caused by a virus or viral infection. While some viral infections can cause neurological disorders, CJD is a distinct condition caused by a prion.
* **Option B:** This option is incorrect because CJD is not a genetic disorder caused by a mutation in a specific gene. While some genetic disorders can cause prion diseases, CJD is primarily an acquired condition caused by the transmission of an infectious prion.
* **Option C:** This option is incorrect because CJD is not caused by a bacterial infection. While some bacterial infections can cause neurological disorders, CJD is a distinct condition caused by a prion.
**Clinical Pearl / High-Yield Fact**
It's essential to note that CJD is a highly infectious condition, and prions can be transmitted through contact with infected tissue or contaminated medical instruments. This highlights the importance of strict infection control measures in healthcare settings.
**Correct Answer: D. Prion. Abnormally folded prion protein (PrP^Sc).**