While being treated with corticosteroids and methotrexate for rheumatoid arthritis, a 63-year-old man developed livid nodules on his lower arms, hands and feet, as well as fever, necrotizing skin ulcers and rupture of a finger extensor tendon.
No vasculitis was found in a biopsy of one of the nodules on the lower arm. Fast growing mycobacteria, classified as M. marinum by PCR, were cultured from wound swabs.
The lesions healed on administration of ciprofloxacin, ethambutol and clarithromycin as well as local treatment.
Cutaneous lesions of an atypical mycobacterial infection are often misdiagnosed. This is especially so in immunocompromised patients and in the differential diagnosis of vasculitis.