One of the rarest and most severe variants of underdevelopment is proximal ectromelia of the lower extremities, in which all segments of the lower limb are affected and the degree of damage decreases from proximal to distal direction. A review of the domestic and foreign literature sources that describe the various clinic-radiological variants of pathology was carried out, from the presence of a single rudimentary foot adjacent to the trunk to the presence of all three leg segments. The terminological designations of this type of underdevelopment were then analyzed. The term proximal ectromelia is proposed as the most appropriate clinical and radiological features of the pathology. With a severe degree of reduction of the limb, when the femur is absent or sharply hypoplastic, prosthetics is carried out in almost all patients. In this situation, surgical treatment is used as a preparatory stage to optimize the design of the future prosthesis. In addition, surgery is the main method of treatment in cases with a lighter degree of underdevelopment, in which case the technical means of rehabilitation are auxiliary. Therefore, despite the relative rarity of this pathology, its severity and medical and social significance determine the interest of specialists of the world community in the study of the problem.