A rare congenital complex vascular malformation syndrome characterized by overgrowth of a limb (most commonly a leg) involving bones and soft tissue, in association with capillary malformations usually in the form of port-wine stains and multiple arteriovenous fistulas with high-flow arteriovenous shunting. The latter can also lead to other severe complications including abnormal bleeding and heart failure. Lymphatic malformations may also be present.