Infection-related Glomerulonephritis and C3 Glomerulonephritis - Similar Yet Dissimilar: A Case Report and Brief Review of Current Literature.

Infection-related glomerulonephritis (IRGN) is an immune complex-mediated glomerulonephritis (GN), often preceded by infection with subsequent recovery of renal function after the resolution of the infection. C3 deposition in the absence of immune complex deposits can be seen in patients with IRGN, but with the emergence of C3 glomerulonephritis (C3GN), the distinction is difficult as the clinical and pathological presentation may be similar. However, their treatment and clinical course vary significantly. A 64-year-old man with a history of hypertension and bioprosthetic aortic valve presented to the Emergency Department with left upper quadrant (LUQ) pain and a purpuric rash on bilateral lower extremities. The patient became septic, and further workup during the hospitalization revealed endocarditis secondary to Streptococcus viridans. On admission, the patient had acute kidney injury (AKI) with a serum creatinine of 3.79 mg/dl, which peaked at 5.72 mg/dl during the hospitalization. Renal biopsy demonstrated segmental necrotizing glomerulonephritis on light microscopy, predominant C3 deposition on immunofluorescence (IF) staining, and mesangial and paramesangial deposits on electron microscopy. This histologic picture can be seen both in IRGN and C3GN. The patient was treated with intravenous ceftriaxone for six weeks for endocarditis and the kidney injury was managed with supportive care. The patient's renal function improved and complement levels normalized, supporting the diagnosis of IRGN retrospectively. IRGN can mimic C3GN, and evaluation for alternate pathways of the complement system may be warranted in patients with atypical presentation of IRGN.