Telangiectasias ( /tɛlˌæn.dʒiː.ɛkˈteɪ.zi.ə/) or angioectasias are small dilated blood vessels near the surface of the skin or mucous membranes, measuring between 0.5 and 1 millimeter in diameter. They can develop anywhere on the body but are commonly seen on the face around the nose, cheeks, and chin. They can also develop on the legs,specifically on the upper thigh, below the knee joint, and around the ankles. Many patients who suffer with spider veins seek out the assistance of physicians who specialize in vein care or peripheral vascular disease. These physicians are called phlebologists or interventional radiologists
Some telangiectasia are due to developmental abnormalities that can closely mimic the behaviour of benign vascular neoplasms. They may be composed of abnormal aggregations of arterioles, capillaries, or venules. Because telangiectasias are vascular lesions, they blanch when tested with diascopy.