CXCL10 in blood finally peaked when BKPyV DNAuria and DNAemia concomitantly occurred with clinical manifestations (significant decoy cell levels ± eGFR decrease) and/or histological evidence of PVAN (median increase: 145.00 pg/ml, 95% CI: 120.20–227.83, P < 0.0001). The gene discussed is CXCL10; the disease is BK-virus nephropathy.