The patient is a 45-year-old IV drug user who presents with fevers, chills, hematuria, and fatigue. On laboratory testing, he was found to have a creatinine of 4.8. Complement levels are depressed and blood cultures are positive. A transesophageal echocardiogram confirmed the presence of endocarditis. A kidney biopsy was obtained due to hematuria.

Image 1 and Image 3 shows circumferential cellular crescents with fibrinoid necrosis (many intracapillary neutrophils are seen in image 3). Figure 2 shows severe interstitial fibrosis. Images 4 and 5 show immunofluorescence staining with IgM and C3, respectively.

This is a case of endocarditis-associated glomerulonephritis with diffuse crescent formation. Contrary to infection-associated glomerulonephritis in general, the most common pattern of glomerular injury in infective endocarditis-associated glomerulonephritis is necrotizing and crescentic glomerulonephritis. ANCA-associated glomerulonephritis enters the differential and up to 28% of endocarditis-associated glomerulonephritis has positive ANCA serology. The strong staining for both IgM and C3 is more commonly seen in endocarditis-associated glomerulonephritis as compared to pauci-immune mediated glomerulonephritis. The most common comorbidities associated with endocarditis-associated glomerulonephritis are cardiac valve disease, intravenous drug use, hepatitis C, and diabetes. Treatment relies on antibiotics plus immunosuppressive therapy and in some cases surgical replacement of cardiac valves.

https://www.ncbi.nlm.nih.gov/pubmed/25607109