A 5-MONTH-OLD BOY had asymmetry of his lower extremities since birth. He was born at term, birth weight 3470 g, to a gravida 6 mother whose pregnancy was unremarkable. The parents were nonconsanguineous, and the family history was unremarkable for similar findings. On physical examination, the left lower limb was 3 cm longer and the circumference larger than that of the right side (Figure 1). An extensive nevus flammeus and livedo reticularis pattern was present on the trunk and extremities, more pronounced on the right side of the chest, with diffuse involvement of the face (Figure 2). A diffuse bluish discoloration was present over the back, the right lateral chest wall, and the lower extremities (Figure 3). Findings from the remainder of the examination were unremarkable.