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Post-injection involutional lipoatrophy: Ultrastructural evidence for an activated macrophage phenotype and macrophage related involution of adipocytes.

We describe a 53-year-old white female with distinctive clinical and histologic changes of involutional lipoatrophy on the right elbow that developed 6 months following a steroid injection to the site. Morphologically, immunohistochemically and ultrastructurally macrophages were seen in close proximity to the altered adipocytes. The macrophages displayed an activated phenotype and were observed engulfing segments of altered adipose and stromal tissue. Other inflammatory cells were lacking and up-regulation of the intra-epidermal Langerhan cells and dermal dendrocytic populations were not observed suggesting non-immune causal mechanisms in the disease process. We believe that the progression model of involutional lipoatrophy is similar to that of glomerulonephritis in which macrophage accumulation can result from non-immune mechanisms such as trauma and lead to the production of several cytokines that induce tissue injury and subsequent fibrosis and sclerosis.