Pathological diagnoses differed by ancestry, with South Asian donors more likely to have progressive supranuclear palsy pathology and Ashkenazi Jewish donors more likely to have Lewy body disease (p < 0.0001), independent of <i>GBA1</i> and <i>LRRK2</i> mutation status.<h4>Conclusion and relevance</h4>Our findings highlight the value of integrating genetic and pathological data to improve diagnostic accuracy. This evidence concerns the gene LRRK2 and Lewy body dementia.