Atypical cutaneous mycobacteriosis caused by M. fortuitum acquired in domestic environment

A previously healthy caucasian woman, 54 years old, came to dermatology outpatient clinic with an erythematous nodulocystic lesion, about 2 cm, with no drainage ostium, located on the dorsal surface of the 4th finger; associated with pain, edema and warmth (Fig. 1). The injury arised four days after local trauma while cleaning her home bathroom. She denied fever, or systemic symptom. There was no improvement despite the use of oral antibiotics and corticosteroids. The hypothesis of pheohyphomycosis, sporotrichosis and atypical mycobacteriosis were considered. Biopsy of the lesion and culture of the liquid content were performed. The anatomopathological analysis showed an organized chronic inflammatory process, occupying the entire thickness of the dermis, but without the presence of fungi and acid-fast bacilli -AFB (Fig. 2). Mycobacterium fortuitum was isolated from sample culture on Middlebrook 7H12. Serologies for HIV, hepatitis B and C, and syphilis were all negative. After confirmation of the etiologic agent, treatment with clarithromycin (1 g/day) and levofloxacin (1 g/day) was implemented, with posterior change of this last medication to sulfamethoxazole-trimethoprim (1200 mg/240 mg every 12 h), due to gastrointestinal intolerance, leading to complete regression of lesion after 6 months (Fig. 3). Atypical mycobacteria, also known as MOTT (mycobacteria other than tuberculosis), are acid-fast bacilli with slow growth in culture and very peculiar behavior. MOTT may be saprophytic or found in animals, water and moist places. Atypical mycobacterioses correspond to 10% of mycobacterial infections and preferentially affect immunocompromised individuals. The rapidly growing mycobacteria (RGM), known by their one-week culture growth, can be found in various sites. The most relevant