Abstract
Vasculitides are a heterogeneous group of primary disorders which may occur secondary to a variety of conditions. Among them, vasculitis caused by bacterial infection is rare. Here, we present images of CT scans and histology from a 22-year-old young Chinese man with vasculitis secondary to bacterial infection, which is a difficult disease to diagnose. This patient had been diagnosed with antineutrophil-cytoplasmic-antibody-negative vasculitis with pulmonary and renal involvement and was treated with glucocorticoids combined with immunosuppressive agents. However, during his follow up we found that multiple patchy shadows and cavities in both lungs and renal lesions had fluctuated, and the improvement of chest imaging was always related to antibiotic treatment. In addition, renal histology showed capillary loop necrosis and extensive crescent formation, and electron microscopy revealed scattered subepithelial hump-like deposits, which favored the diagnosis of infection over idiopathic vasculitis. Therefore, vasculitis secondary to infection was confirmed. The subsequent therapy response supported our diagnosis. This case is important; since vasculitis secondary to infection is uncommon, our case provides a model for the diagnosis of vasculitis secondary to infection.