LRRK2 and Parkinson disease: The question remains as to why one-third of LRRK2 PD patients do not show α-synuclein pathology at autopsy19 and have a negative α-synuclein seeding amplification assay test.12 This is important to understand as anti-α-synuclein based treatment strategies could potentially lack efficacy in a subset of LRRK2 G2019S carriers and/or these patients may not meet eligibility criteria to enter trials and test new therapies.