Superimposed glomerular immune complexes in anti-glomerular basement membrane disease

The association of anti-glomerular basement membrane (GBM) antibody-mediated glomerulonephritis and glomerular immune complexes is common and probably arises from a number of mechanisms. In the series, glomerular immune complexes were identified in 6 of 17 patients who initially presented with anti-GBM disease. In four cases, glomerular immune complexes were noted in renal biopsies obtained at clinical presentation; in the other two, they were first demonstrated seven and 28 months after presentation, when circulating anti-GBM antibody levels were undetectable. Circulating immune complexes were detected in only two of six patients, either 28 months before or 17 months after the demonstration of the glomerular membranous lesion. The association of glomerular immune complexes and anti-GBM disease may be coincidental with immunologically-unrelated immune complexes localizing in the GBM for physico-chemical reasons; or the presence of glomerular-bound anti-GBM antibodies may predispose to the deposition of molecules with particular affinity for these antibodies. One patient with glomerular immune complexes used heroin, which may be associated with immune complex formation and the development of glomerulonephritis; and one patient was subsequently thought to have systemic lupus erythematosus (SLE). An antecedent infection was found in two of the four patients who had glomerular complexes at presentation, but in only three of 13 with uncomplicated anti-GBM disease. Three of 6 patients with superimposed glomerular complexes had a history of exposure to organic solvents before the onset of disease, while none in the group with anti-GBM disease alone had.