All are true about Huntington’s disease except:
**Core Concept**
Huntington's disease (HD) is a rare, autosomal dominant neurodegenerative disorder characterized by the expansion of a CAG repeat in the huntingtin gene. This leads to the production of a mutant protein that causes progressive damage to the basal ganglia, particularly the caudate nucleus and putamen.
**Why the Correct Answer is Right**
Huntington's disease is indeed associated with the expansion of CAG repeats in the huntingtin gene, leading to the production of a mutant protein that causes neuronal degeneration. The disease is characterized by chorea, psychiatric symptoms, and cognitive decline. The basal ganglia, particularly the caudate nucleus and putamen, are affected, leading to motor symptoms such as chorea and rigidity.
**Why Each Wrong Option is Incorrect**
**Option A:** This statement is true about Huntington's disease. HD is indeed an autosomal dominant disorder, meaning that a single copy of the mutated gene is sufficient to cause the disease.
**Option B:** This statement is true about Huntington's disease. The disease is characterized by progressive neuronal degeneration, particularly in the basal ganglia, leading to motor symptoms such as chorea and rigidity.
**Option C:** This statement is true about Huntington's disease. HD is indeed associated with psychiatric symptoms, such as depression, anxiety, and psychosis.
**Clinical Pearl / High-Yield Fact**
Huntington's disease is a classic example of a neurodegenerative disorder caused by an expansion of a CAG repeat in a gene. This expansion leads to the production of a mutant protein that causes neuronal degeneration and progressive damage to the basal ganglia.
**Correct Answer: A. This statement is not true about Huntington's disease.**