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Background: Infective endocarditis (IE)-associated rapidly progressive glomerulonephritis (RPGN) is rarely reported. Sporadic case reports have noted the diagnostic and therapeutic challenge in IE-associated glomerulonephritis because it may masquerade as idiopathic vasculitis., Methods: Patients with clinical diagnosis of IE-related RPGN in a tertiary hospital in China between January 2004 and May 2021 were identified and retrospectively reviewed., Results: Twenty-four patients with IE-associated RPGN were identified. All patients presented with fever and multiorgan system involvement on top of heart and kidneys, spleen (79%, 19/24), skin (63%, 15/24), lung (33%, 8/24) and nervous system (17%, 4/24). Six of the 24 patients (25%) were initially suspected to have ANCA-associated or IgA vasculitis. Forty-five percent of patients are seropositive for ANCA. Renal histology showed mesangial and/or endocapillary hypercellularity with extensive crescents in most patients. C3-dominant deposition was the predominant pattern on immunofluorescence and pauci-immune necrotising crescentic glomerulonephritis was observed in one case. All patients received antibiotics with or without surgery. Six patients received immunosuppressive therapy before antibiotics due to misdiagnosis and seven patients received immunosuppressive therapy after antibiotics due to persistence of renal failure. Three of the 24 patients died due to severe infection. All the surviving patients had partial or complete recovery of renal function., Conclusion: IE-associated RPGN is rare and the differential diagnosis from idiopathic vasculitis can be challenging due to overlaps in clinical manifestations, ANCA positivity and absence of typical presentations of IE. The prognosis is generally good if antibiotics and surgery are not delayed. The decision on introducing immunoruppressive treatment should be made carefully on a case by case basis when kidney function does not improve appropriately after proper anti-infective therapy.Key messagesInfective endocarditis associated RPGN is rare and differentiating it from idiopathic vasculitis can be challenging due to overlap in clinical manifestations, ANCA positivity and occasional absence of typical manifestations of infective endocarditis.Kidney function usually responds to antibiotic therapy alone.Immunosuppressive therapy may be beneficial in carefully selected patients whose kidney function does not improve with antibiotics alone.

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. [ABSTRACT FROM AUTHOR]

Background: Purpura and glomerulonephritis are typical presentations in IgA vasculitis. Infective endocarditis mimicking IgA vasculitis by presenting with glomerulonephritis and purpura is rarely reported.Methods: We searched for cases with infective endocarditis-associated purpura and glomerulonephritis in a tertiary hospital in China and retrospectively reviewed their clinicopathological features. Differential diagnosis and treatment in patients with infective endocarditis-associated purpura and glomerulonephritis were discussed.Results: A total of 20 cases with infective endocarditis-associated purpura and glomerulonephritis were identified among 548 cases with infective endocarditis in our center during an 8-year period: 7 of the 20 cases (35%) were initially misdiagnosed as IgA vasculitis and 10 cases (50%) presented with left-sided endocarditis caused by Streptococcus viridans. Fever (100%, 20 out of 20), prior valvular deformities (80%, 16 out of 20), cardiac murmur (95%, 19 out of 20), splenomegaly (84%, 16 out of 19), embolism (55%, 11 out of 20), and hypocomplementemia (76%, 13 out of 17) were present in most patients. Crescents and mesangial hypercellularity with or without endothelial hypercellularity were the primary findings on light microscopy, with C3-dominant deposition on immunofluorescence. But IgA-dominant staining was also observed (40%, 2 out of 5). In patients with rapidly progressive glomerulonephritis, patients with complete recovery of renal function had shorter disease duration and higher ratio (67% vs 20%) of immunosuppressive therapy compared with patients with partial recovery.Conclusions: Infective endocarditis-associated glomerulonephritis and purpura can closely mimic IgA vasculitis. Differential diagnosis is challenging, particularly when typical presentations of infective endocarditis are absent. In adults with presentations like IgA vasculitis, infective endocarditis should be evaluated through comprehensive clinical and pathological investigations. Immunosuppressive therapy can be considered in patients with severe glomerulonephritis who do not improve after proper anti-infective therapy. [ABSTRACT FROM AUTHOR]