[Bursitis due to Mycobacterium intracellulare in an immunocompetent patient]

Cutaneous infections due to Mycobacterium intracellulare are infrequent. We report a case of bursitis in an immunocompetent patient.

A 80-year-old patient with a history of tuberculosis reported swelling of the elbow for six months with effusion due to olecranon bursitis, progressing to an abscess and skin ulceration. Examination of the synovial fluid revealed the presence of M. intracellulare. Histologic investigations showed epithelioid and gigantocellular granulations. Screening for immunodepression was negative. Treatment with clarithromycin and rifabutin proved effective, with partial healing at three months, although hepatic and ocular side effects occurred.

While osteomyelitis, arthritis and cutaneous infections due to M. intracellulare have been described in immunocompromised patients, there are very few reported cases concerning immunocompetent individuals, and these suggest the possibility of special individual sensitivity to mycobacterial infections. Genetic mutations of the interleukin-12-interferon-gamma pathway involved in the immune response to mycobacterial infections have been demonstrated. Autoantibodies against interferon-gamma have also been described. Mycobacterium avium-intracellulare is resistant to the classical antibiotics used in tuberculosis. As in pulmonary infections, antibiotics with proven in vivo and in vitro efficacy must be used, taking into account the antibiogram and potential side effects, particularly for combined clarithromycin and rifabutin.

This case report emphasizes the benefits of routine mycobacterial investigation of synovial fluid samples.