The histopathology of localized lipoatrophy.

We studied 11 patients with the clinical diagnosis of lipoatrophy and found two histopathological subsets. Six patients presented with a distinctive picture, which we termed 'involutional' fat, consisting of lobules of small lipocytes embedded in hyaline connective tissue with numerous capillaries. Five of these six patients had a single lesion, usually of the upper arm. Serological studies were normal, and direct immunofluorescence, performed in three cases, showed immunoreactants in the blood vessels in only one. The four patients with inflammation of the fat had multiple areas of localized lipoatrophy. Three had biopsies for direct immunofluorescence and all three showed immunoreactants involving the basement membrane zone (two cases) or blood vessels (one case); and three had serological abnormalities. We suggest that the involutional histopathological pattern is a distinctive subset of localized lipoatrophy.