Infective Endocarditis-Associated Pauci-Immune Crescentic Glomerulonephritis with Complete Remission after Immunosuppression

Introduction: Kidney disease due to infective endocarditis (IE) was first described over 100 years ago. Although initially believed to be primarily embolic, it later became clear that majority of cases represented focal, segmental, or diffuse proliferative glomerulonephritis. Currently, the most common kidney biopsy findings in IE are necrotizing and crescentic GN (~50%), followed by endocapillary proliferative GN (~40%). We describe a rare case of crescentic GN in the setting of renal limited PR3 ANCA Vasculitis (AAV) in a patient with Streptococcus mitis aortic valve (AV)infective endocarditis with complete renal recovery after valve replacement and immunosuppression. Case Description: 24-year-old male with asthma presented with fevers, chills, and weight loss. Workup revealed bicuspid AV and aortic vegetation. Blood cultures were persistently negative, and he had no prior h/o IV drug use. He received antibiotic therapy, underwent mechanical AV replacement with lifelong anti-coagulation deemed necessary. PCR testing of native AV revealed Streptococcus Mitis. Despite source control and AV replacement, patient developed RPGN. Cr 4.7 mg/dL, Sr albumin 2.3 g/dL, UPCR 2519 mg/g, urinalysis revealed acanthocytes. C3 48 (low), C4 13. PR-3 25. Rest of comprehensive serological workup (incl. Anti-GBM) negative. Kidney biopsy revealed crescentic GN that was pauci-immune with no immune complex or electron dense deposits. Given source control of IE with antibiotics and valvular replacement, induction immunosuppression (IS) with intravenous cyclophosphamide [total - 3g] and glucocorticoids [pulse followed by oral taper] lead to serological remission of AAV [BVAS=0] and complete kidney function recovery with no further RBCs in the urine. He received intravenous rituximab [5 doses of 500 mg so far] for remission maintenance with no flare-ups so far. Discussion: IE related pauciimmune crescentic GN carries a poor prognosis with a mortality rate of 40-50%. Outcomes have not really improved over time. Treatments have ranged from isolated antibiotic use [~ 60%] and antibiotics with supportive care [35%]. Data on use of IS is lacking and often shows mixed results. Through our case, we postulate the role of IS after early source control has been attained, especially in young patients with no other comorbidities.