[Nocardiosis, an important opportunistic infection].

In three patients, a 69-year-old woman, a 52-year-old woman and a 35-year-old man, nocardiosis was diagnosed. The first woman had chronic B-cell leukaemia and mucosal pemphigoid; she was on immunosuppressive medication, and had fever and a suppurative arthritis of the knee. The second woman was on immunosuppressive medication following a kidney transplantation and had fever and a pulmonary infiltrate. The male patient had hereditary cystic kidneys and a soft tissue infection of the left leg. He was not immunologically compromised. Nocardiosis is mainly an opportunistic bacterial infection but can also affect immune competent patients. The disease manifestations are protean, ranging from localised skin infections to severe systemic diseases, quite often with central nervous system involvement. Identifying the organism can be challenging, and notifying the laboratory when nocardiosis is suspected can help to optimise the diagnostic yield. Nocardiosis requires a long duration of medical therapy, trimethoprim-sulfonamide being the most frequently used antibiotic combination.