Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Klippel-Trenaunay syndrome ?
    ### Response:
    Klippel-Trenaunay syndrome is a condition that affects the development of blood vessels, soft tissues, and bones. The disorder has three characteristic features: a red birthmark called a port-wine stain, abnormal overgrowth of soft tissues and bones, and vein malformations.
    