关键词:

Abstract: This case involved a 10-year-old female patient who presented with a 46-day history of intermittent fever and cough. Chest computed tomography（CT） revealed multiple thick-walled cavitary lesions and nodular opacities in both lungs. Polymicrobial bacterial infection was identified by etiological testing，and the provisional diagnosis was pneumonia with lung abscess. The patient's condition initially improved after anti-infective therapy but relapsed rapidly，with the subsequent gradual development of multisystem involvement manifestations including anemia，oral ulcers，skin rashes and purpura. After 58 days of complicated diagnosis and treatment，the patient was definitively diagnosed with granulomatosis with polyangiitis（GPA） via vasculitis-related antibody testing，skin tissue biopsy，and multidisciplinary team（MDT）consultation. The core value of this case lies in revealing the atypical onset characteristics of rare pediatric autoimmune diseases，highlighting the diagnostic challenges when infection is intertwined with autoimmune lesions，and emphasizing the importance of multidisciplinary collaboration，dynamic monitoring of inflammatory markers and timely completion of specific examinations in avoiding misdiagnosis.

Key words: lung abscess, pneumonia, childhood systemic vasculitis, ANCA-associated vasculitis, granulomatosis with polyangiitis