We previously reported the presence of immunoglobulin A (IgA) antineutrophil cytoplasmic antibodies (ANCAs) in patients presenting IgA nephropathy (IgAN), particularly when associated with Henoch-Schonlein purpura. Most of the patients exhibited IgA ANCAs directed at an unknown 50-kd neutrophil protein but no IgG ANCAs. A subgroup of patients presented IgG as well as IgA ANCAs, suggesting an overlap syndrome between Henoch-Schonlein purpura and microscopic polyangiitis. We aimed at confirming the correlation of IgA ANCA titer with disease activity in a patient presenting IgAN relapse following kidney transplantation. The ANCAs were searched for by isotype- and antigen-specific enzyme-linked immunosorbent assay. Specificity was confirmed by antigen-specific enzyme-linked immunosorbent assay and Western blot analysis. At the onset of the disease in 1989, the patient presented with ANCAs of IgA and IgG class with specificity for myeloperoxidase and no rheumatoid factor. End-stage renal failure developed 1 year afterward. In 1991, he received a cadaveric renal allograft, and 9 months later developed acute nephrotic syndrome with rapidly progressive renal failure and recurrence of IgAN on the kidney transplant. An increase in IgA but not IgG ANCAs was found on clinical relapse after kidney transplantation. We conclude that rare patients may present an overlap syndrome between IgG ANCA-positive systemic vasculitis and IgAN, characterized by the presence of IgG and IgA anti-myeloperoxidase antibodies.