A 70-year-old man with progressive dementia has autopsy findings of neurofibrillary tangles in the entorhinal cortex and hippocampus, amyloid plaques, and cortical atrophy. The protein within neurofibrillary tangles is:
- A Alpha-synuclein forming Lewy bodies
- B Hyperphosphorylated tau (microtubule-associated protein) forming paired helical filaments ✓
- C TDP-43 forming cytoplasmic inclusions
- D Mutant huntingtin forming intranuclear inclusions
Explanation
Neurofibrillary tangles (NFTs) in Alzheimer disease consist of paired helical filaments (PHF) of abnormally hyperphosphorylated tau protein. Tau normally stabilizes microtubules; hyperphosphorylation dissociates tau from microtubules, impairing axonal transport, and the free tau aggregates into PHF. Braak staging tracks NFT progression from entorhinal cortex → hippocampus → association cortices → primary cortices. Alpha-synuclein forms Lewy bodies in Parkinson disease and DLB. TDP-43 inclusions occur in ALS and FTLD-TDP. Huntingtin intranuclear inclusions are pathognomonic of Huntington disease.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.