Immunopathogenesis of Syphilitic Glomerulonephritis

A renal biopsy was performed on a patient with syphilitic glomerulonephritis characterized clinically by the acute onset of nephrosis that responded dramatically to penicillin therapy. Histologic, electron microscopical and immunohistochemical studies revealed an early membranous glomerulonephritis characterized by the presence of subepithelial basement-membrane deposits containing IgG and C3. The glomerular lesion, however, differed from that in the usual case of membranous nephropathy in that distinctive segmental lesions were present at the tubular poles of the glomeruli, and all the glomeruli exhibited mild proliferation of mesangial cells in association with the presence of IgM within mesangial areas. Antibody elution studies performed on the renal-biopsy specimen demonstrated the presence of antitreponemal antibody within the glomerular immune-complex deposits. This finding indicates that the glomerular injury occasionally complicating secondary syphilis is due to the deposition of treponemal antigen-antitreponemal antibody complexes.