Skin and joint infection by Mycobacterium chelonae: rescue treatment with interferon gamma

Abstract

Introduction: Atypical mycobacteria are environmental organisms that cause opportunistic infections in humans.

Case report: A 50-year-old electronics engineer sought advice about starting TNFalpha antagonist therapy for ankylosing spondylitis. Disease duration was 23 years and current treatment was methylprednisolone 4 mg/d. Atypical skin lesions and knee arthritis were noted. Fluid aspirated from the knee showed inflammatory properties and a few acid-fast bacteria, which a line probe assay identified as Mycobacterium chelonae. The same organism was found in a skin biopsy from a thigh lesion. Antimicrobial treatment was started immediately. Inadequate results 6 months later prompted synovectomy of the knee followed by interferon gamma, 50 microg/m(2) body surface area subcutaneously 3 times a week. After 16 months, there were no new skin or joint lesions, and the antimicrobials and interferon gamma were therefore discontinued.

Conclusion: This highly unusual case suggests that interferon gamma may be effective in patients with M. chelonae infection that fails to respond adequately to antimicrobials.