Coexistence of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and IgA nephropathy

Co-occurrence of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and IgA nephropathy (IgAN) is extremely uncommon. To date, only a few case reports have described such patients. Here, we describe the clinical presentation, pathologic features, treatment response, and outcome data of five patients with the rare form of co-existing AAV and IgAN and compared the characteristics of these patients to AAV patients with pauci-immune glomerulonephritis (n = 10) and IgAN patients (n = 10) that were selected as controls by stratified random sampling. In addition, we summarize all the previously reported cases of AAV and IgAN. In total, including the current study, 16 AAV/IgAN overlap cases were reported. Our five patients with the coexistence of AAV and IgAN were younger than the ten AAV patients with pauci-immune glomerulonephritis (22.6 ± 8.2 years versus 48.9 ± 15.7 years, respectively, P = 0.004). Histologically, they had a significantly lower percentage of glomeruli with fibrous crescents compared with AAV patients (0.0% versus 4.0%, P = 0.038). Compared with ten IgAN patients, our five AAV/IgAN patients had higher levels of ESR (P = 0.032) and CRP (P = 0.031). After accepting treatment with a combination of steroid and immunosuppressants, all patients showed a positive response to therapy, except for one patient in our cohort and another previously reported patient. We described the clinical presentation, pathologic features, treatment response, and outcome data of five patients with overlapping AAV and IgAN. They had mild glomerular pathological lesions and a positive response to aggressive immunosuppressive therapy. They were quite similar to pauci-immune AAV patients in clinical features, except for younger age. They had a lower percentage of glomeruli with fibrous crescents compared with AAV patients. In contrast to IgAN patients, they had higher levels of ESR and CRP. The mechanism of the coexistence of IgAN and AAV needs further study.