Describe the pathogenesis of the atypical mycobacteria.

Often the diagnosis is delayed because of the varied clinical and histopathologic findings. After inoculation, there is an incubation period of 1 to 29 weeks. Classically, this is followed by an eruption of painful nodules that increase to 2 to 5 cm in size, and which then drain purulent fluid for 7 to 14 days before forming a scar over 1-month period. Other skin lesions have been reported including folliculitis, furuncles, abscesses, cellulitis, nodules, draining lesions, ulcers, and fistulae. Granulomatous infiltrate, diffuse lymphohistiocytic infiltrate, mixed inflammatory infiltrate, granulomas rheumatoid nodules, abscesses, panniculitis, and folliculitis have been observed in biopsy specimens. Staining for acidfast bacteria with Fite or auramine-rhodamine is often unrevealing. Thus the current gold standard is skin biopsy for tissue culture followed DNA sequencing.

Regnier S, Cambau E, Meningaud JP, et al: Clinical management of rapidly growing mycobacterial cutaneous infections in patients after mesotherapy, Clin Infect Dis 49(9):1358–1364, 2009.

Drage LA, Ecker PM, Orenstein R, et al: An outbreak of Mycobacterium chelonae infections in tattoos, J Am Acad Dermatol 62:501– 506, 2010. [Epub ahead of print.]