| A syndrome affecting the development of blood vessels, soft tissue and bone with three characteristic features: port-wine stain, abnormal overgrowth of soft tissues and bones and venous malformations. Caused by mutations in the PIK3CA gene. This gene provides instructions for making the p110 alpha (p110α) protein, which is a subunit of phosphatidylinositol 3-kinase (PI3K). The PIK3CA gene mutations associated with Klippel-Trenaunay syndrome alter the p110α protein. The altered subunit makes PI3K abnormally active, which allows cells to grow and divide continuously. Increased cell proliferation leads to abnormal growth of the bones, soft tissues, and blood vessels. This syndrome is almost always sporadic meaning it can occur in people with no history of the disorder in their family. Studies suggest that the condition results from gene mutations that are not inherited. |
