Coexistence of antineutrophil cytoplasmic antibody-associated vasculitis and membranous nephropathy: a case report.

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and membranous nephropathy (MN) are two types of diseases that can both involve kidneys. In recent years, there are some reports about the concurrence of these two diseases. However, the precise mechanism, clinical course, and optimal treatment of patients with this unusual combination of renal diseases are little known. Previously reported cases of MN combined with AAV presented characteristics of both MN and crescentic glomerulonephritis, manifesting rapid disease progression and poor prognosis. Diagnosis and treatment are essential and challenging. Here, we report a case of AAV and MN in a 62 years old man, who was admitted to hospital due to edema, low-grade fever, and cough. The patient showed a different pathological feature from previous cases, with no crescent formation. By analyzing the diagnoses and potential pathogenesis, we considered MN was secondary to the present AAV and suspected the existence of other alternative mechanisms. Also, we applied a new therapy, glucocorticoid with mizoribine. After one-year follow-up, this treatment is feasible, safe, and leads to a clinical improvement for AAV combined with MN. In this case, two diseases overlapped, and the laboratory analysis and pathology are both required to ensure diagnostic accuracy. The principal aim of this case report is to highlight the diagnostic challenge and distinct treatment in the simultaneous occurrence of AAV combined with MN.