We identified a cis-pQTL that is associated with decreased levels of serum GPNMB (transmembrane glycoprotein NMB; rs7797870; MAF = 0.4286; P = 7.01 × 10−50; BETA = −0.2109; SE = 0.0247) and colocalises with a known Parkinson’s disease (PD) locus32 (CLPP4 = 0.86) (Fig. 4b). The gene discussed is GPNMB; the disease is Parkinson disease.