While most PD biomarker discovery approaches focus on data from idiopathic PD (IPD) patients, an interesting alternative approach using an integrative analysis of whole-blood gene expression data from IPD patients, familial PD patients with the LRRK2 G2019S mutation and different mouse models was presented by Chikina et al. (2015). The gene discussed is LRRK2; the disease is Parkinson disease.