In the present study, we investigated the expression of claudin-1 and its colocalization with ZO-1 in various human glomerular diseases including IgA nephropathy, purpura nephritis, ANCA associated vasculitis (MPO-ANCA and PR-3 ANCA), anti-GBM-RPGN, and lupus nephritis. The gene discussed is CLDN1; the disease is rapidly progressive glomerulonephritis.