Tau protein pathology is central to several neurodegenerative diseases. In Alzheimer's disease, tau forms neurofibrillary tangles predominantly composed of hyperphosphorylated tau with which isoform predominance?

• A 4R tau predominantly (as in PSP and CBD)
• B 3R tau predominantly (as in Pick's disease)
• C 2R tau exclusively (fetal isoform)
• D 3R + 4R tau in equal proportions (mixed isoform tangles) ✓

Explanation

Neurofibrillary tangles (NFTs) in Alzheimer's disease contain hyperphosphorylated tau with an equal mixture of 3-repeat (3R) and 4-repeat (4R) isoforms, distinguishing them from primary tauopathies. Progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) feature 4R tau predominance, while Pick's disease features 3R tau predominance. This isoform ratio has diagnostic and pathobiological implications for tauopathy classification.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.