Klippel-Trenaunay syndrome is a congenital peripheral vascular disorder whose etiology remains unclear, but is generally thought to be related to vascular malformations due to abnormal mesodermal development. The main manifestations of this disease are in the extremities, especially in the lower extremities, with some lesions involving the buttocks, waist, lower abdomen or shoulders, usually involving one limb. The main manifestations: 1.Superficial varicose veins of the lower extremities, the occurrence of which is different from the general superficial varicose veins of the lower extremities, mainly concentrated in the outer part of the thighs or buttocks, and the veins are usually raised inconspicuously. 2.Wine stain, a kind of map-like slightly elevated light red or purplish-red nevus, which can fade when pressed, is actually an intradermal vascular nevus, which is the characteristic manifestation of the disease and is often mistaken as birthmark by parents. 3.The growth or thickening of one limb, as the child grows, the limb on the affected side will gradually grow and thicken. 4. Increased skin temperature of the affected limb. Comparison of the limbs on both sides reveals that the temperature of the affected limb is slightly higher. There are mainly the following types: ① venous type – mainly venous abnormalities, including superficial varicose veins, venous aneurysms, deep venous valve insufficiency, deep venous valve deficiency or deep venous deficiency, etc.; ② arterial type – including arterial blockage, deficiency or abnormal hyperplasia, etc. Arterio-venous fistula type – mainly based on the abnormal arterio-venous fistula of the affected limb; ③ mixed type. The main hazards: Due to the vascular malformation, the affected limb is oversupplied with blood and develops more than the opposite limb, which can lead to soft tissue and bone hypertrophy, limb growth and thickening, and in severe cases, the limbs on both sides are of different lengths, causing the child to limp, and long-term limp will affect spinal development and form scoliosis, and the imbalance of force on the bilateral hip joints may cause strain on the hip joints. In individual cases, because the arteriovenous fistula is close to the trunk, it leads to ischemic changes in the distal limb, which is manifested as cold, pale or purple at the end of the limb, and in severe cases, it can lead to blackness and necrosis at the end. The varicose veins can develop thrombosis secondary to slow blood flow, forming thrombotic superficial phlebitis, which is characterized by redness, pain, increased local skin temperature and pain when touched along the veins. There is no special treatment method, mainly symptomatic reduction treatment. If the limb length difference exceeds 1.5cm, the heel of the healthy side can be padded to prevent secondary lesions caused by long-term limping. For the thickening of the affected limb, medical elastic stockings or elastic bandages should be used for compression therapy, which can control varicose veins, reduce the heaviness and swelling of the lower limbs caused by venous stasis, and prevent the occurrence of thrombotic superficial phlebitis. For the superficial varicose veins with normal function of deep veins and valves, local varicose shallow injection of sclerotherapy or laser treatment can be performed. For children with arteriovenous fistula or bilateral limbs of unequal length, bilateral arteriograms of lower limbs can be performed first, and if abnormal vessels are found, they can be embolized or surgically ligated in order to retard the development of the affected limbs and reduce claudication. For children with cavernous hemangioma, hemangioma sclerotherapy is feasible.