This pilot immunohistochemistry study assessed peptidylarginine deiminase isozymes (PAD1, PAD2, PAD3, PAD4 and PAD6) and protein deimination in post-mortem human brains with incidental Lewy body disease and Parkinson’s disease (PD) at Braak stages 4–6. Here, PADI6 is linked to Lewy body dementia.