BACKGROUND Disease activity and treatment-related toxicity are the most important contributors to poor prognosis in patients with ANCA-associated vasculitis (AAV). Sometimes, it is difficult to distinguish them. We present a case to highlight the challenges in the management of AAV and the complications with immunosuppression. An 81-year-old female patient presented to our institution with gross hematuria, fatigue, nausea, anorexia, and progressively deteriorating renal function. ANCA enzyme

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... unoassay revealed a perinuclear staining pattern (p-ANCA) and serum anti-myeloperoxidase (MPO) antibody titer of 119 units/ml. She initially improved with intravenous methylprednisolone. However, after tapering the glucocorticoids and starting cyclophosphamide, her appetite and general state worsened, with increased body temperature, but serum creatinine and C-reactive protein concentrations and the erythrocyte sedimentation rate keep being decreased. Intravenous immunoglobulin and antibiotics had no effect. Intensive immunosuppressive therapy was initiated, and just as she improved, she suddenly developed purulent and bloodtinged sputum. Computed tomography of the chest showed a solid nodule with cavitation in the dorsal segment of the left lower lobe. Sputum culture revealed growth of Mucor species. Amphotericin B liposomes (LAMB) were administrated, and the cumulative dosage was 2.0 g with 2 months' treatment duration. Finally, repeat sputum culture was negative, the nodular lesion disappeared, and only a cystic air space remained. No nephrotoxicity with LAMB was seen. Comprehensive dynamic evaluation is important for patients with AAV. The subjective symptoms and objective indicators are not fully parallel, and manifestations between disease activity and treatment-related adverse reactions are often similar. Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of chronic multisystem autoimmune diseases with substantial mortality and morbidity and frequent relapses. AAV is characterized by predominant small