ITSN1 and Parkinson disease: Carriers of GBA1 and LRRK2 variants were selectively recruited to the AMP-PD cohort.19 To determine if the overrepresentation of these individuals downwardly biased the association between PD and ITSN1, we reperformed the association test excluding carriers with likely pathogenic GBA1 or LRRK2 variants (n = 701 excluded cases, n = 1,560 excluded controls).