LOCALIZED INVOLUTIONAL LIPOATROPHY - A CLINICOPATHOLOGICAL STUDY OF 16 PATIENTS

Background: Localized loss of adipose tissue without antecedent clinic al or histologic inflammation is termed idiopathic lipoatrophy. Object ive: Our purpose was to study the clinical and pathologic features in 16 patients with clinically focal lipoatrophy and a distinct pathologi c pattern of fat lobule involution. Methods: A retrospective study of 16 patients was performed. Results: The buttocks and proximal extremit ies were involved most frequently. Lesions were solitary in 10 patient s and multiple in six. Nine patients had received intramuscular or int raarticular corticosteroid or antibiotic injections in the affected ar eas before the development of lipoatrophy. Histologic examination show ed that individual fat cells were decreased in size and separated by h yaline material. Progressive reduction in the size and number of adipo cytes resulted in diminutive fat lobules with prominent vessels resemb ling embryonic fat lobules. Some adipocyte masses were acidophilic. Sc attered macrophages, confirmed by immunoperoxidase staining for CD68 ( KP-I), were identified within the fat lobules and surrounding connecti ve tissue. Yellow-gray granules were recognized within the cytoplasm o f macrophages in nine cases. Macrophages becoming lipophages were obse rved by electron microscopy in one case. Other inflammatory cells were not prominent. Conclusion: This is a common pattern of postinjury res ponse to fat tissue characterized by macrophage infiltration of the fa t lobules in variable numbers. The term involutional lipoatrophy is ju stified by the resemblance of the distinctive pathologic changes to em bryonic fat lobules.