Histopathological examination of the substantia nigra in a patient who died with a 12-year history of parkinsonism shows depigmentation of the pars compacta and eosinophilic cytoplasmic inclusions in surviving neurons. What protein constitutes these inclusions?

• A Tau
• B TDP-43
• C Alpha-synuclein ✓
• D Ubiquitin only, without a specific protein

Explanation

Parkinson disease is defined pathologically by loss of dopaminergic neurons in the substantia nigra pars compacta with Lewy bodies, which are eosinophilic cytoplasmic inclusions whose principal component is alpha-synuclein. Tau accumulation characterises progressive supranuclear palsy and corticobasal degeneration, the commonest parkinsonian mimics. TDP-43 inclusions define frontotemporal lobar degeneration and amyotrophic lateral sclerosis, not idiopathic Parkinson disease.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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