Disseminated cat-scratch disease during abatacept therapy for rheumatoid arthritis in an older patient: A case report and review of the literature.

Cat-scratch disease (CSD) is a zoonotic infection primarily caused by Bartonella henselae following cat scratches. It typically presents with localized skin symptoms and self-limiting lymphadenopathy; however, in some cases, it can progress to disseminated lesions, leading to severe complications. We report a case of CSD with multiorgan involvement in a 79-year-old woman undergoing abatacept treatment for rheumatoid arthritis. She presented with persistent fever and painful right axillary lymphadenopathy, accompanied by induration on the right hand caused by a cat scratch. Imaging studies revealed multiple enlarged lymph nodes as well as hepatosplenic and cervical spine lesions. Initially, the patient was clinically diagnosed with CSD and initiated on azithromycin monotherapy; however, her symptoms persisted. A right axillary lymph node biopsy was performed to re-evaluate the diagnosis. Histopathological analysis showed numerous necrotizing granulomas with multinucleated giant cells, and a polymerase chain reaction assay confirmed the presence of B. henselae in the lymph node, establishing the diagnosis of CSD with multiorgan involvement. Treatment was adjusted to an azithromycin and rifampicin combination, resulting in a gradual improvement in symptoms. CSD may present as a fever of unknown origin with extranodal involvement affecting organs, such as the liver, spleen, bones, and central nervous system, or causing infective endocarditis, complicating the diagnosis. In immunosuppressed patients receiving biological agents for rheumatic diseases, a comprehensive evaluation is crucial. This should include a detailed medical history, physical examination, and comprehensive histological and microbiological assessments to differentiate CSD from conditions such as tuberculosis and malignant lymphoma.