[The 512th case: fever, cough, acute kidney injury].

A 70-year-old female patient presented with fatigue and edema for 3 months and was found to have elevated serum creatinine for 3 weeks. During the course of the disease, she had fever and cough. Examinations revealed multiple ground-glass opacities in both lungs and positivity for myeloperoxidase-anti-neutrophil cytoplasmic antibodies (ANCA), leading to a diagnosis of ANCA-associated vasculitis. The patient's condition initially improved after pulse glucocorticoid therapy combined with cyclophosphamide. During treatment, however, the patient developed hematochezia, and colonoscopy revealed multiple colonic ulcers. Immunohistochemistry of colonic mucosal biopsy confirmed cytomegalovirus (CMV) positivity, establishing a diagnosis of CMV colitis. The patient was found to have concurrent Clostridioides difficile and pulmonary infections. During the disease course, the patient also developed deep vein thrombosis and roxadustat-associated central hypothyroidism. Given the presence of multiple comorbidities, rituximab was subsequently used for vasculitis treatment, resulting in sustained remission. This case highlights the importance of highly individualized treatment strategies for older patients with vasculitis, requiring adjustment of immunosuppressive therapy intensity based on disease progression.