The use of biological drugs, which include among others anti-tumour necrosis factor α antibody therapy (ATNFαT), may be related to increased incidence of bacterial, viral and fungal infections. Inhibition of the immune system changes the clinical course of infection compared to immunocompetent individuals. Usually an infection has a tendency to generalize or to a symptomless course of the disease. A case of a 60-year-old woman suffering from aggressive rheumatoid arthritis (for 12 years), diabetes mellitus, treated with adalimumab, methotrexate and prednisone with a diagnosis of abscess of the right lower leg soft tissue with aetiology caused by Salmonella sp. is presented (Fig. 1, 2). Appearance of infiltration was preceded by fever. The therapy applied included antibiotics in compliance with antibiogram and surgical treatment (drugs acting as topical disinfectants, accompanied by a regular change of drains), giving a very good clinical effect (Fig. 3) as a result of immunosupresive drugs use. The emergence of the abscess was probably preceded by symptomless Salmonella infection and bacteraemia. One should also take into account the possibility of a carrier-state and reactivation of latent infection. During diagnosis and treatment methotrexate and adalimumab were withdrown. Because of the ever increasing number of patients using biological agents, it is worth noting how unusual course and aetiology an infection may have in these patients. A decision on re-introduction of disease modifying anti-rheumatic drugs or re-qualification of the patient for biological treatment would be taken after the antibiotic therapy is completed.