Within the GSL lipid class, GlcCer(d18:1/24:1) increased by 15% (unadjusted p = 0.07), and lactosylceramide (LacCer) (d18:1/24:1) decreased by 53%, (unadjusted p = 0.07) in LRRK2 variant PD subjects compared to PD patients that do not carry a variant in LRRK2 (Fig. 7A and B, Supplementary Fig. S7B). Here, LRRK2 is linked to Parkinson disease.