In this study, we have analysed LRRK2 dependent pRab10Thr73 phosphorylation as a marker for in vivo LRRK2 activation status in human peripheral blood neutrophils isolated from 101 individuals including 42 LRRK2 mutation carriers (21 with the G2019S mutation that resides in the kinase domain and 21 with the R1441G mutation that lies within the ROC-COR GTPase domain) with and without PD and compared them with 32 healthy controls and 27 individuals with iPD. The gene discussed is LRRK2; the disease is Parkinson disease.