**Core Concept**
Prions are infectious proteins that cause fatal neurodegenerative diseases in animals, including humans. They are unique in that they are the only infectious agents that consist solely of protein, without any nucleic acid. Prion diseases, also known as transmissible spongiform encephalopathies (TSEs), are characterized by progressive neurological dysfunction and death.

**Why the Correct Answer is Right**
Prions are highly resistant to heat, radiation, and chemicals, which makes them difficult to inactivate. They can cause disease through self-replication and accumulation in the brain, leading to neuronal damage and death. The mechanism of prion disease involves the conversion of normal cellular prion protein (PrP^C) to the disease-causing form (PrP^Sc), which is thought to be mediated by a conformational change in the protein structure.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because prions are indeed infectious and can be transmitted between individuals, although the exact mechanism of transmission is not fully understood.
**Option B:** Incorrect because prions are not known to cause cancer, although they can cause significant neurological damage and death.
**Option C:** Incorrect because prions are not currently known to be treatable with any specific medication or therapy, although research is ongoing to develop potential treatments.

**Clinical Pearl / High-Yield Fact**
Prion diseases are unique in that they can be transmitted through contact with infected tissue, such as through surgical instruments or contaminated food products. This highlights the importance of proper infection control and safety protocols in healthcare settings.

**Correct Answer: C. Prions are not currently known to be treatable with any specific medication or therapy, although research is ongoing to develop potential treatments.**