BACKGROUND: The main causative agents of cat-scratch disease are Bartonellahenselae, tiny, gram-negative bacilli. The disease usually has a benign course with the development ofa papule at the inoculation site, followed by regional lymphadenopathy. In most cases, complete resolutionoccurs, but in immunocompromised hosts, the course of the disease can be aggravated. CASE REPORT: A patientreceived methotrexate and corticosteroids for 3 months due to rheumatoid arthritis. He developed fever,exanthema and leukopenia under methotrexate therapy. Dark red indurations with central ulcerations athis right thigh revealed a further problem apart from the methotrexate-induced leucopenia and immunosuppression.The ulcerations were the remainders of recurrent scratches from the patient's cat. The patient's antibodytiters against Bartonella henselae remained low and inguinal lymph node swelling was only for a shorttime to be observed, this reaction obviously weakened as a result of the immunosuppression. However,the typical course, the exclusion of other reasons for the exanthema and the rapid improvement of thepatient's condition after antibiotic treatment ascertained the diagnosis. CONCLUSIONS: In immunocompromisedhosts, diseases with a typically benign course can become severe and life-threatening illnesses. Ownershipof pets should be taken into consideration before onset of an immunosuppressive therapy.

Keywords: Bartonella henselae, Cat-Scratch Disease, Cats, Immunocompromised Host, Immunosuppression, Immunosuppressive Agents