INVOLUTIONAL LIPOATROPHY - MACROPHAGE-RELATED INVOLUTION OF FAT LOBULES

Involutional lipoatrophy is an apparent idiopathic lipoatrophy with ch aracteristic histopathologic features. We report a patient with a dist ant history of intramuscular injections and subsequent typical involut ional lipoatrophy in whom macrophage invasion of the fat was prominent . Light microscopy revealed small, thin lobules of fat with focally pr ominent blood vessels and a variably hyaline background, Macrophages c ontaining granular acid mucopolysaccharide material were present in di rect apposition to lipocytes, around involuting lobules and between co llagen fibers in the neighboring dermis. Focal deposits of iron were o bserved. Electron-microscopic examination revealed macrophages abuttin g lipocytes and containing lipid droplets, clear vacuoles and lysosome s in varying proportions. Lipocytes varied in size. The lipid appeared normal in most, but scattered cells contained electron-dense granules or needle-shaped clefts within the lipid. We speculate that previous injections in our patient stimulated a macrophage response, with subse quent regression of lipocytes of the neighboring fat lobules.