These include:

Bloom syndrome (homozygous null mutation in BLM DNA repair enzyme. similar mechanism and etiology to ataxia telangiectasia)
Naevus flammeus (port-wine stain)
Klippel–Trenaunay syndrome
Maffucci syndrome (multiple enchondromas and hemangiomas)
Hereditary hemorrhagic telangiectasia (Osler–Weber–Rendu syndrome)
Ataxia–telangiectasia
Sturge–Weber syndrome, a nevus formation in the skin supplied by the trigeminal nerve and associated with facial port-wine stains, glaucoma, meningeal angiomas and intellectual disabilities
Hypotrichosis–lymphedema–telangiectasia syndrome, caused by mutation in transcription factor SOX18

Venous hypertension
In the past, it was believed that leg varicose veins or telangectasia were caused by high venous pressure or "venous hypertension". However it is now understood that venous reflux disease is usually the cause of these problems.Telangiectasia in the legs is often related to the presence of venous reflux within underlying varicose veins. Flow abnormalities within the medium-sized veins of the leg (reticular veins) can also lead to the development of telangiectasia. Factors that predispose to the development of varicose and telangiectatic leg veins include

Age
Sex: It used to be thought that females were affected far more than males. However, research has shown 79% of adult males and 88% of adult females have leg telangectasia (spider veins). Pregnancy: Pregnancy is a key factor contributing to the formation of varicose and spider veins. Changes in hormone levels are one of the most important reasons women are more likely to develop varicose veins during pregnancy. There is an increase in progesterone, which causes the veins to relax and potentially swell more easily.
Telangiectasias, also known as spider veins, are small dilated blood vessels that can occur near the surface of the skin or mucous membranes, measuring between 0.5 and 1 millimeter in diameter. These dilated blood vessels can develop anywhere on the body, but are commonly seen on the face around the nose, cheeks and chin. Dilated blood vessels can also develop on the legs, although when they occur on the legs, they often have underlying venous reflux or "hidden varicose veins" (see Venous hypertension section below). When found on the legs, they are found specifically on the upper thigh, below the knee joint and around the ankles. Many patients with spider veins seek the assistance of physicians who specialize in vein care or peripheral vascular disease. These physicians are called vascular surgeons or phlebologists. More recently, interventional radiologists have started treating venous problems. Some telangiectasias 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. Telangiectasias, aside from presenting in many other conditions, are one of the features of the acronymically named CREST syndrome, a form of systemic scleroderma. The syndrome recognises the significantly co-presenting symptoms of calcinosis, Raynauds phenomenon, esophageal dysmotility, sclerodactyly and telangiectasia. Causes
The causes of telangiectasia can be divided into congenital and acquired factors. Genetic
Goldman states that "numerous inherited or congenital conditions display cutaneous telangiectasia".