Triple Threat: Bartonella Endocarditis Unmasking Heart Failure, Nephrotic Syndrome, and Pancytopenia in Repaired Tetralogy of Fallot

Introduction: Blood culture-negative endocarditis (BCNE) presents a critical diagnostic challenge, as delays increase mortality. Bartonella species, a notable cause of BCNE and associated infection-related glomerulonephritis, can be elusive, risking misdiagnosis and detrimental empiric immunosuppression. Case Description: A 37-year-old woman with DiGeorge syndrome and a melody prosthetic pulmonary valve presented with a one-month history of increasing dyspnea, 10 kg weight, and volume overload. Echocardiography revealed new, severe biventricular dysfunction (LVEF 30-35%). Laboratory findings included rising creatinine from 0.8 to 3.3 mg/dL, UPCR 8.7 g/g, albumin 2.2 g/dL, C3 18 mg/dL, C4 2.4 mg/dL and platelet 34 x103/uL. Blood cultures persistently remained negative. Given prosthetic hardware, feline exposure, and hypocomplementemia, Bartonella PCR was performed and returned positive. An FDG PET-CT scan showed focal uptake at the prosthetic valve. Treatment with doxycycline-ceftriaxone, aggressive diuresis, and neurohormonal blockade improved her volume status, and creatinine decreased to 1.6 mg/dL. Renal biopsy was deferred due to thrombocytopenia. Patient elected a self-directed discharge on day 32, continuing oral doxycycline and guideline-directed heart failure therapy. Discussion: This case highlights Bartonella endocarditis as a cause of severe, multi-system BCNE, manifesting with heart failure, nephrotic syndrome, and pancytopenia. Diagnosis relied on ESC criteria, integrating PCR, imaging, and serology, which is crucial when biopsy is contraindicated. Prompt recognition, targeted doxycycline-based therapy, and multidisciplinary management are vital to reverse organ damage and avoid inappropriate immunosuppression.18F- FDG PET-CT shows increased uptake in prosthetic pulmonic valve