A 70-year-old patient has progressive dementia with alpha-synuclein-positive Lewy bodies in the substantia nigra AND cortex, and Alzheimer-type pathology. According to current neuropathological criteria, concurrent Lewy body pathology in the presence of high Alzheimer disease neuropathological change (ADNC) is classified as:

• A Pure dementia with Lewy bodies (DLB) — the Alzheimer pathology is incidental
• B Parkinson disease dementia — cortical Lewy bodies are always classified as PDD
• C Prion disease — alpha-synuclein is a surrogate marker for CJD
• D Mixed pathology: both high ADNC and Lewy body pathology contribute to the cognitive phenotype ✓

Explanation

Co-occurrence of Lewy body pathology and Alzheimer disease neuropathological change (ADNC — defined by Thal amyloid phase, Braak NFT stage, and CERAD neuritic plaque score) is extremely common in older adults. Current National Institute on Aging/Lewy body pathology consensus guidelines classify such cases as having mixed pathology, where both pathological processes likely contribute to the clinical dementia syndrome. Neither is simply 'incidental' — high ADNC reduces the threshold for Lewy body pathology to produce clinical symptoms. This mixed pathology represents a significant proportion of late-life dementia.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.