Could you explain what is klippel trenaunay weber syndrome?

Blood vessel malform: Rare congenital medical condition in which blood vessels and/or lymph vessels fail to form properly. The three main features are nevus flammeus (port-wine stain), venous and lymphatic malformations, and soft-tissue hypertrophy of the affected limb. Often called angio-osteohypertrophy or hemangiectatic hypertrophy and is found as a congenital defect at time of birth in many cases.