The levels of urinary C3a (8.97, 0.41–67.72 vs. 0.01, 0.00–0.01 ng/mg Cr, P<0.001), C5a (18.69, 1.00–185.91 vs. 0.03, 0.01–0.05 ng/mg Cr, P<0.001), and soluble C5b-9 (59.49, 7.73–216.68 vs. 0.64, 0.07–1.33 ng/mg Cr, P<0.001) were significantly higher in patients with primary FSGS than that in normal controls (Fig 1). Here, C5 is linked to focal segmental glomerulosclerosis.