PO119 | BARTONELLA HENSELAE INFECTION ASSOCIATED WITH A MULTISYSTEMIC THROMBO-INFLAMMATORY SYNDROME IN AN IMMUNOCOMPETENT ADULT

G. Gobbo^1|2, M. Zacchia^1|2, F. Nalesso^1|3, M. Fedrigo^1|4, S. Da Pozzo⁵, L. Frison⁷, F. Vianello^1|6, A. Angelini^1|4, P. Simioni^1|2, A. Hoxha^1|2 | ¹Department of Medicine - DIMED, University of Padua, Italy; ²Internal Medicine Unit, Thrombotic and Bleeding Disorder Center; ³Nephrology Unit; ⁴Pathology Unit; ⁵Radiology Unit; ⁶Hematology Unit, University-Hospital of Padua, Italy; ⁷Hematology Unit, Ospedale dell’Angelo, Mestre, Italy

Background. Bartonella henselae is a Gram-negative intracellular bacterium classically associated with cat-scratch disease, a usually self-limited condition characterized by regional lymphadenitis. However, occasionally may lead to severe systemic manifestations, particularly in immunocompromised hosts.
Case reports. Here we report, a previously healthy 43-year-old man presented in Emergency Department on April 2023 with abdominal pain, rectal bleeding, low-grade fever, and severe thrombocytopenia (19×10⁹/L). Abdominal CT revealed ileocolic intussusception, splenic ischemic lesions, hepatomegaly, and retroperitoneal lymphadenopathy (Fig. 1A), leading to urgent right hemicolectomy. Six days later, a CT scan performed as diagnostic workup showed pulmonary embolism with deep vein thrombosis (Fig. 1B). Treatment with intravenous immunoglobulin and corticosteroids resulted in partial platelet recovery. A vena cava filter was placed, and anticoagulation with apixaban was initiated. In May 2023, the patient experienced recurrent fever and migratory arthritis and was treated with a two-week course of prednisone and antibiotics, with improvement. Four weeks later, arthritis recurred and blood tests showed acute kidney injury with nephrotic-range proteinuria and recurrent thrombocytopenia. Physical examination showed mild bilateral exophthalmos and ocular motility impairment. A brain MRI demonstrated multiple microembolic ischemic lesions. Fluorescein angiography and Optical coherence tomography showed abnormalities, suggestive of secondary serous retinal detachment. Laboratory testing revealed elevated inflammatory markers and lupus anticoagulant positivity, while autoimmune screening, ADAMTS-13 activity, and extensive infectious work-up were initially negative. Complement levels were within the normal range. The patient received prednisone and was then transferred to a tertiary center. There, he recalled a recent exposure to purulent material from an infected pet dog. Expanded microbiological testing detected Bartonella henselae DNA by whole-blood PCR. Retrospective histopathological review of the surgical showed small-vessel endothelial inflammation and thrombosis compatible with infection-associated microangiopathy (Fig. 1C-E). Cardiac MRI demonstrated inflammatory cardiomyopathy, and renal MRI showed inflammatory renal injury. Targeted antimicrobial therapy with doxycycline was initiated and extended to five weeks due to persistent PCR positivity. Corticosteroids were gradually tapered and anticoagulation was maintained. Clinical improvement followed antimicrobial therapy, with normalization of platelet counts, stabilization of renal function, regression of thrombotic manifestations, and, eventually, PCR negativity. Lupus anticoagulant testing at 12 weeks was negative. The patient remained asymptomatic at the latest follow-up visit on March 2026.
Conclusions. This case describes a severe multisystem thrombo-inflammatory syndrome associated with B. henselae infection in an immunocompetent adult. The clinical picture initially suggested CAPS or other primary TMAs. However, available laboratory findings did not support a diagnosis of overt microangiopathic hemolysis. Bartonella species exhibit endothelial tropism and may promote vascular inflammation and prothrombotic phenomena. Bartonella infection should be considered in patients with unexplained TMA-like presentations, particularly when routine investigations remain inconclusive.