Overlapping IgA and membranous nephropathy.

Four patients with overlapping IgA nephropathy and membranous nephropathy recently have been reported from two different medical centers in Japan. The authors describe two patients from the United States with the concurrence of IgA and membranous nephropathy and a third patient who may have the same overlapping glomerular lesions. All three patients had hematuria and nephrotic range proteinuria. Renal biopsy specimens from two of the patients revealed focal proliferative glomerular lesions, large mesangial and numerous subepithelial electron-dense deposits, exclusively mesangial intense immunostaining for IgA, and extensive granular capillary wall immunostaining for IgG. The third patient is a sibling of one of the other patients and was shown to have focal proliferative glomerular lesions, mesangial immunostaining for IgA, and numerous subepithelial electron-dense deposits. Pathogenic possibilities are discussed.