A 65-year-old man develops resting tremor, rigidity, bradykinesia, and postural instability. Biopsy of the substantia nigra would reveal depletion of dopaminergic neurons and intracytoplasmic eosinophilic inclusions. These inclusions are immunoreactive for which protein?

• A Tau
• B Huntingtin
• C Alpha-synuclein ✓
• D Amyloid precursor protein

Explanation

The intracytoplasmic inclusions are Lewy bodies, which are the pathologic hallmark of Parkinson disease. They consist of a dense eosinophilic core surrounded by a pale halo on H&E staining and are immunoreactive for alpha-synuclein and ubiquitin. Substantia nigra pars compacta dopaminergic neuronal loss causes the clinical features of Parkinsonism. Mutations in SNCA (alpha-synuclein gene) cause rare familial forms, underscoring its central pathogenic role.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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