Sub acute – Sclerosing pan – encephalitis (SSPE) is caused by
**Core Concept**
Subacute sclerosing panencephalitis (SSPE) is a rare chronic and progressive neurological disorder caused by a persistent infection with a mutant form of the measles virus. This condition primarily affects children and young adults, leading to severe cognitive and motor impairments.
**Why the Correct Answer is Right**
SSPE is caused by a defective measles virus that has accumulated mutations over time, resulting in a persistent and chronic infection. This defective virus is unable to replicate efficiently, leading to the accumulation of viral particles and the activation of the immune system, which in turn causes inflammation and damage to the brain. The measles virus targets the oligodendrocytes, leading to demyelination and the characteristic pathological features of SSPE.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as SSPE is not caused by a bacterial infection. While bacterial infections can cause a range of neurological disorders, SSPE is a viral disease.
* **Option B:** This option is incorrect as SSPE is not caused by a prion disease. Prion diseases, such as Creutzfeldt-Jakob disease, are caused by misfolded proteins and are distinct from viral infections.
* **Option D:** This option is incorrect as SSPE is not caused by a fungal infection. Fungal infections can cause a range of neurological disorders, but SSPE is a viral disease.
**Clinical Pearl / High-Yield Fact**
SSPE is a rare but devastating neurological disorder that can be prevented through measles vaccination. The measles vaccine is highly effective in preventing SSPE, and widespread vaccination has led to a significant decline in the incidence of this disease.
**Correct Answer:** C.