Mycobacterium chelonae Cutaneous Infection: An Important Differential Diagnosis in the Immunosuppressed Patient with Chronic Ulcers.

In 2018, a 38-year-old woman was referred to our hospital with some nodules and nonhealing ulcers on her left thigh that had been present for 18 months. Her medical history included rheumatoid arthritis (RA) being treated with 20-mg prednisone for the last 8 years. There was no history of trauma, surgery, or cosmetic procedure on the leg. Physical examination revealed multiple lesions on her left thigh, including nodules, surrounded by erythema, some of them being covered with a fine white-yellowish scale and hyperpigmented macules. Central atrophy was evident in some lesions. She also had one ulcer with purulent discharge (Figure 1). An infectious disease and vasculitis were considered in the differential diagnoses. Biopsy and culture were conducted from the lesion. A Ziehl-Neelsen stain was obtained from the ulcer's discharge with visible acid-fast bacilli (Figure 2). Light microscopy examination revealed a mixed granuloma with lymphocytes, neutrophils, and giant cells in the dermis (Figure 3). The culture was positive for M. chelonae sensitive to clarithromycin. Treatment with clarithromycin was initiated (500 mg, twice a day) for 8 weeks, with healing of some of the lesions. She was advised to continue antibiotic treatment for 4 more weeks and to report to our hospital after its completion, but she never returned and was lost on follow-up.