How do Huntington disease and Parkinson disease differ in inheritance, primary movement abnormality, and typical age of onset?

• A. Huntington disease is autosomal recessive with chorea; onset in 60s; Parkinson disease autosomal dominant with tremor
• B. Huntington disease is autosomal dominant with chorea and psychiatric symptoms; onset typically in the 30s–40s; Parkison disease usually sporadic or familial with bradykinesia/rigidity/tremor
• C. Huntington disease is X-linked with dystonia; onset in childhood; Parkison disease only in women
• D. Huntington disease is sporadic; Parkinson disease autosomal dominant with bradykinesia

Answer: (B)

The main idea tested is how Huntington disease and Parkinson disease differ in how they run in families, what movement problems they produce, and when they usually begin. Huntington disease is inherited in an autosomal dominant manner due to a CAG-repeat expansion in the HTT gene, and it classicly presents with chorea and psychiatric or cognitive symptoms. Its typical onset is in the 30s to 40s, not in the 60s. Parkinson disease, on the other hand, is usually not tied to a single dominant inheritance pattern; most cases are sporadic, though there are familial forms. Its dominant movement features are bradykinesia with rigidity and resting tremor, and it tends to begin after about age 60. The description that Huntington disease is autosomal dominant with chorea and psychiatric symptoms and that onset is typically in the 30s–40s, while Parkinson disease is usually sporadic or familial with bradykinesia/rigidity/tremor, best matches these differences. The other options mix incorrect inheritance patterns and onset ages (for example, Huntington as recessive or X-linked, or Parkinson as strictly autosomal dominant), making them less accurate.