A congenital vascular bone syndrome with the presence of a vascular malformation in a limb, mainly of the arteriovenous type, which results in overgrowth of the affected limb. The affected limb may show overgrowth in comparison with the contralateral limb and the extent of this limb length discrepancy may vary from a slight difference to 10cm or more. The growth effect may be manifested in only one bone (mainly the femur or tibia) or, in some cases, affect the whole limb. The existence of arteriovenous fistulas around or inside the bone is now being widely accepted as the main cause of bone overgrowth. Although the syndrome generally appears to be sporadic, autosomal dominant inheritance has been noted in a few families.