Among the many hazards of intrauterine development and sojourn is failure at times to achieve complete congenital integrity of the integument. It sometimes happens that a child is born with a superficial erosion, as in Fig. 27-1, or an ulcer, as in Figs. 27-2 and 27-3. The vertex of the scalp is a common place for the phenomenon to occur; the hands, face, and points over bony prominences are also susceptible. Aplasia cutis congenita is frequently a benign event of only cosmetic importance, and in most cases the etiology is not established. However, epidermolysis bullosa, placental infarction, teratogens, and some chromosome deletions and trisomies are occasionally implicated as causes. A lesion may be directly adjacent to an epidermal nevus or nevus sebaceus, or it may overlie a defect in the bone. More significant underlying anomalies are meningomyeloceles, spinal dysraphisms, and various cerebral malformations. Hemorrhage and secondary infection may occur, requiring emergency treatment. The combination of aplasia cutis congenita and distal limb reduction is an additional inherited disorder.