Natural History of Injectable Permanent Synthetic Filler Disease

Injectable permanent synthetic filler disease is characterized by heterogeneous local and systemic manifestations that may emerge years after filler injection. Although inflammatory reactions, migration, foreign-body granulomas, adipose tissue injury, fat necrosis, and fibrosis have been individually described, the temporal clinicopathologic evolution of the disease remains poorly characterized. This prospective observational cohort study aims to characterize the natural history of disease associated with injectable permanent synthetic fillers by integrating time since injection, clinical manifestations, magnetic resonance imaging findings, and histopathologic tissue features. Participants with a history of gluteal injection of permanent synthetic fillers who undergo clinical evaluation, magnetic resonance imaging, and clinically indicated surgical removal of affected tissue will be evaluated. Histopathologic findings will be systematically assessed for adipose tissue injury, acute and chronic inflammation, foreign-body granulomatous reaction, fat necrosis, fibrosis, characteristics of the exogenous material, and vascular or lymphatic involvement. The primary objective is to determine how histopathologic disease patterns vary according to time since injection. Secondary objectives include evaluating temporal associations with clinical symptoms, extent of migration on magnetic resonance imaging, fibrosis, granulomatous inflammation, and evidence of superimposed inflammatory reactivation.