The attempt to reshape and enhance the buttocks through injected substances has emerged as a significant public health concern, leading to mortality, morbidity, and substantial healthcare costs. This chapter comprehensively explores the pathophysiology, clinical presentation, treatment objectives, and approaches based on the deformity associated with this practice. We introduce the terms “allogenic megapygia” and “allopygia” to describe deformities that may involve cutaneous, subcutaneous, and local muscular components, with lymphatic extensions to other body compartments adjacent or distant to the gluteal area.