Atypical post‐infectious glomerulonephritis with c‐ANCA positivity followed by endocarditis

Post‐infectious glomerulonephritis (PIGN), an uncommon variety of glomerulonephritis (GN), is characterized by emergence of nephritic syndrome within a few weeks following an infectious event. PIGN typically presents as a mild condition and tends to resolve by the time of diagnosis for GN. Aggregatibacter actinomycetemcomitans belongs to the HACEK group of bacteria, which constitutes less than 3% of bacteria responsible for community‐acquired infective endocarditis. We present a case of 29‐year‐old man suspected of lymphoma with B‐symptoms along with severe splenomegaly and nephromegaly. Shortly after, he developed an episode of nephritic syndrome accompanied by acute kidney injury (AKI) and high titers of cytoplasmic ANCA (c‐ANCA)‐positivity. Kidney biopsy revealed PIGN with tubulointerstitial nephritis. Despite treatment with antibiotics and corticosteroid, he visited the emergency room due to worsening dyspnea and multi‐organ failure. An echocardiogram showed a bicuspid aortic valve with vegetation unseen on previous echocardiogram. He underwent aortic valve replacement immediately without adverse events. Four months after valve replacement, his renal function and cardiac performance have remained stable. We report a case of PIGN with AKI and high titers of c‐ANCA appearing later as an infective endocarditis due to Aggregatibacter actinomycetemcomitans. With careful clinical observation and appropriate and timely management, satisfactory outcomes for patient health are possible.