This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Klippel-Trenaunay syndrome (KTS) is a syndrome that affects the development of blood vessels, soft tissues, and bones. This syndrome has three characteristic features: a red birthmark called a port-wine stain, overgrowth of soft tissues and bones, and vein malformations such as varicose veins or malformations of deep veins in the limbs. The overgrowth of bones and soft tissues usually begins in infancy and is most often only affects one leg. However, it can also affect the arms or sometimes the upper body area (torso). The overgrowth can cause pain, a feeling of heaviness, and make the affected leg (or arm) hard to move.
Most, if not all, cases of KTS are caused by somatic mutations in the PIK3CA gene. Medical researchers believe KTS is part of a group of disorders known as PIK3CA-related overgrowth spectrum (PROS) which also includes MCAP and CLOVES syndromes, hemimegalencephaly, fibroadipose hyperplasia, and epidermal nevus. Treatment is symptomatic and supportive.
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