A 45-year-old man develops progressive choreiform movements and cognitive decline. Genetic testing reveals an expanded trinucleotide repeat on chromosome 4. Which brain structure shows the most severe atrophy in this condition?

• A Substantia nigra
• B Globus pallidus
• C Hippocampus
• D Caudate nucleus ✓

Explanation

Huntington disease is caused by CAG repeats in the huntingtin gene on chromosome 4. It causes severe atrophy of the caudate nucleus and putamen, leading to the clinical triad of chorea, dementia, and psychiatric symptoms. Substantia nigra atrophy is seen in Parkinson disease.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.