Abstract
RATIONALE: Systemic lupus erythematosus (SLE) and anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) are 2 different diseases that can manifest in the same person, which are known as SLE/AAV overlap syndrome. This overlap syndrome is difficult to diagnose, a high rate of missed diagnosis and misdiagnosis, and a poor prognosis. PATIENT CONCERNS: A 52-year-old woman was diagnosed with SLE in 2019. She was readmitted to our hospital in October 2021 because of abdominal pain and melasma for 10 days. DIAGNOSES: She had positive anti-dsDNA, decreased complement C3 and C4, fever, polyarthralgia, and hemolytic anemia. She was diagnosed as microscopic polyangiitis according to the American College of Rheumatology 2022 AAV classification criteria (she had 4 items: no nasal lesions, eosinophils < 1 × 109, negative c/PR3-ANCA antibodies, and positive p-ANCA antibodies. The score was 6 points). INTERVENTIONS: The patient was treated with methylprednisolone 200 mg and cyclophosphamide 0.2 g immunosuppressive therapy. OUTCOMES: After 2 months of follow-up, the patient's symptoms, including abdominal pain, melena, hematuria, and hemoptysis, resolved completely. And she underwent a reexamination of chest computed tomography and the results showed the previous exudation had been absorbed. LESSONS: AAV should be considered in lupus patients with the above symptoms, especially the progressive decrease of hemoglobin. Relevant examinations are needed to confirm the diagnosis. Early diagnosis and accurate treatment of SLE/AAV overlap syndrome are beneficial to patients' better prognosis and control the treatment cost.