ANCA-associated vasculitis combined with coexisting Aspergillus fumigatus and Mycobacterium avium complex infections: a case report

BACKGROUND: Existing studies indicate that infection may serve as both initiators and accelerators in the pathogenesis of Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) through multiple immunopathological pathways. We report a rare case of AAV combined with two fatal infections of Aspergillus fumigatus and Mycobacterium avium complex (MAC), in which a successful clinical outcome was achieved. CASE PRESENTATION: A 67-year-old female with a history of bronchiectasis was admitted due to poor appetite and fatigue, along with newly identified renal insufficiency. Her serum creatinine levels progressively increased, and urinalysis revealed hematuria and proteinuria. A clinical diagnosis of Aspergillus fumigatus and Mycobacterium avium complex (MAC) infections was made based on the combination of high-resolution computed tomography (HRCT) imaging, results of next-generation sequencing (NGS) in bronchoalveolar lavage fluid (BALF), and serological tests, taking into account the pre-existing bronchiectasis. AAV was diagnosed by serum test and kidney biopsy. Treatment included anti-fungal therapy, glucocorticoids, plasma exchange, and immunoglobulin pulses, without immunosuppressants. The patient’s lung infection and renal function improved remarkably, but dissemination of the MAC infection occurred. Consequently, we added anti-MAC therapy. Along with the improvement of the lung lesion, the AAV also achieved complete remission without relapse during follow-up. CONCLUSION: This case highlights the novelty of the simultaneous occurrence of AAV, invasive aspergillosis, and MAC infection. We hypothesize that chronic infections in the context of bronchiectasis may have acted as a trigger for ANCA production and the subsequent development of vasculitis. Further investigations are necessary to determine whether the infection acts as a trigger or an accompanying phenomenon. CLINICAL TRIAL: Not applicable.