We present a case of a 22-month-old child with swollen upper part of the right arm and osteolytic lesion of the right humerus, which resembled a neoplastic process. Epidemiological history revealed no scratch marks on the skin or cutaneous papule or pustule. Presumptive diagnosis of hematogenous osteomyelitis was established, but treatment with fusidic acid was unsuccessful. Histological examination of the bioptic specimen of the soft tissue swelling showed a lymph node morphology, with numerous granulomas with central stellate necrosis. Indirect immunofluorescence assay for Bartonella henselae yielded positive results. New treatment included 15 days of trimetoprime and sulfamethoxazole, followed by azithromycin for 5 days. Four months later, swelling resolved and osteolytic lesion almost completely healed with formation of surrounding sclerosis. In conclusion, cat-scratch disease without positive epidemiological history and primary cutaneous papule or pustule may be a serious diagnostic problem, but can be solved by serological and histological examination.