PCSK1N and Parkinson disease: Conversely, our Lewy body copathology rates may be underestimated because the sensitivity of α‐synuclein SAAs are limited in low Braak stages of Lewy body pathology,19 or it may be possible that the detection of α‐synuclein pathology via SAA is inhibited by the presence of tau pathology, noting that one of our pathologically diagnosed PSP participants with Braak stage 1 Lewy body copathology was PD‐type SAA negative.