Locus minoris resistentiae: Mycobacterium chelonae in striae distensae

Rachel M Greenwood, Morgan W Thakore, Loretta S Davis
2020 Cutis (New York, N.Y.)  
Immunosuppressed patients are at particular risk for disseminated mycobacterial infections. A locus minoris resistentiae offers less resistance to the infectious spread of these microorganisms. We present a case of Mycobacterium chelonae infection preferentially involving striae distensae. A 30-year-old man with chronic eosinophilic pneumonia requiring high-dose corticosteroid therapy presented with widespread skin lesions. He reported no history of cutaneous trauma or aquatic activities.
more » ... c activities. Physical examination revealed the patient was markedly cushingoid with generalized cutaneous atrophy and widespread striae. Multiple erythematous papules surrounded a large ulceration on the dorsal aspect of the left hand. Depressed erythematous plaques and several small crusted erosions extended up the left lower leg (Figure 1 ) to the knee. Strikingly, numerous brown and pink papules and small plaques on the left thigh were primarily confined within striae (Figure 2) . A biopsy of the left thigh revealed granulomatous inflammation (Figure 3 ) with numerous acid-fast bacilli • Striae distensae, seen frequently in the setting of chronic corticosteroid use, are at an increased risk for localized infection, particularly in immunocompromised patients. There should be a low threshold to biopsy striae distensae that demonstrate morphologic evolution. • The Koebner reaction, also known as an isomorphic response, refers to the appearance of certain dermatoses in previously healthy skin subjected to cutaneous injury. • Locus minoris resistentiae is an isotropic response that characterizes the presentation of a new dermatosis within an area previously affected by an unrelated skin condition that has healed. FIGURE 1. Erythematous depressed plaques with scale and a few crusted erosions on the anterior aspect of the lower leg.
doi:10.12788/cutis.0083 pmid:33104127 fatcat:lf5f5r6nxrgcfezx2w67d6yqfa