What are the symptoms? The port wine stain is a flat, red or purple mark on the skin that is often the only noticeable symptom of Klippel-Trenaunay syndrome at birth. Varicose veins are generally seen along the length of the limb. The symptoms associated with varicose veins, like swelling and aching of the leg, can be reduced by wearing support stockings from an early age. There is a small risk of blood clots developing in patients with Klippel-Trenaunay syndrome. A specialist will provide appropriate advice. The increased growth of the limb is not always noticeable at birth and needs to be monitored in early childhood. The limb can be increased in girth and length. The main functional problem relates to leg length and it is therefore important to be seen regularly by an orthopaedic surgeon if the leg length difference is significant. This becomes of concern if it is greater than 2.5 cm. In this situation, it is possible to stop the longer leg growing when the child is about 11 to 13 years old by a straightforward operation called epiphysiodesis, allowing the shorter leg to catch up. Rarely leg length asymmetry can affect the lower spine and cause backache. Klippel-Trenaunay syndrome can be part of a more extensive complex blood vessel/lymphatic malformation. It may be associated with bleeding, for example, rectal bleeding if it involves the pelvis. It can cause significant discomfort of the limb and reduced mobility. What are the causes? The cause is genetic but the genetic defect of Klippel-Trenaunay syndrome has not as yet been identified, therefore genetic testing is not part of diagnosis. How is it diagnosed? Diagnosis is based on clinical features and most cases require ultrasound and magnetic resonance imaging (MRI), both techniques that allow images of the inside of the body to be viewed, to more accurately define the extent of the blood vessel abnormality. How is it treated? Medical care needs to be tailored to the individual patient and requires multidisciplinary management involving orthopaedics in relation to leg length inequality, compression bandages, laser treatment for the port wine stain, surgical intervention if appropriate and psycho-social support. The varicose veins may be helped by sclerotherapy, which involves the injection of a sclerosant liquid to chemically seal the enlarged veins. Inheritance patterns and prenatal diagnosis Inheritance patternsThe condition occurs sporadically as a congenital/developmental abnormality and does not seem to run in families. Prenatal diagnosisNone. Is there support? Information and support in the UK for Klippel-Trenaunay syndrome is provided by the Proteus Family Network (see entry Proteus syndrome).