involutional lipoatrophy involutional lipoatrophy involutional lipoatrophy is a cutaneous condition, and is an idiopathic lipoatrophy characterized clinically by non-inflammatory focal loss of fat. involutional lipoatrophyspecialtydermatology idiopathic localized involutional lipoatrophy (ilil) is a rare and nosologically imprecise condition characterized by a focal loss of subcutaneous tissue on one or several sites, occurring without any significant triggering factor or auto-immune background, and regressing spontaneously within a few months.