Clinicopathological features of antineutrophil cytoplasmic antibodies-associated vasculitis in Japanese patients with IgA nephropathy

Antineutrophil cytoplasmic antibodies (ANCA) have been reported to be associated with systemic vasculitis. However, the roles of ANCA subtypes in patients with IgA nephropathy remain to be fully investigated. We describe three Japanese patients with IgA nephropathy complicated by ANCA-associated vasculitis. Two patients with IgG class ANCA developed rapidly progressive renal failure and demonstrated mesangial proliferation with extensive extracapillary proliferation and segmental glomerular necrosis. One patient with IgM class ANCA showed severe extrarenal symptoms, such as lung fibrosis and neuritis, in addition to glomerular crescent formation. All three patients received immunosuppressive therapies, including corticosteroids and cyclophosphamide. The two patients who received these treatments early showed improvement in urinary protein excretion and renal function, in accordance with a decrease in the serum titer of ANCA. However, one patient in whom serum creatinine was already elevated showed a poor response to the treatment. These results suggest that ANCA subtypes may participate in the pathogenesis of crescent formation in patients with IgA nephropathy, and that early treatment with a combination of methylprednisolone pulse therapy, oral prednisolone, and cyclophosphamide pulse therapy may be beneficial in these patients.