Unilateral nevoid telangiectasia (UNT) is a cutaneous condition consisting of congenital or acquired patches of superficial telangiectases in a unilateral linear distribution. Described in 1899 by Blaschko, its segmental pattern suggests a mechanism of somatic mosaicism apparent early in life or unmasked in states of relative estrogen excess, such as that in pregnancy or in chronic liver disease.
Vascular malformations may result from a somatic mutation during embryologic development giving rise to distinct cell populations in a single individual. Paradominant inheritance, in which an autosomal mutation results in loss of heterozygosity and gives rise to a mosaic patch or twin spots, may explain the rare occurrence of telangiectatic nevi in several family members. [1, 2] Whether these alterations include different concentrations of receptors for vasoactive substances or hormones remains to be determined. Telangiectasias are almost always limited to the skin, and associated gastric telangiectasias reported in one case may have been due to the underlying hepatic dysfunction.
A review of the literature by Wilkin et al in 1983 described 46 reported cases  ; according to Hynes, 100 cases were reported by 1997.  However, as a benign condition, unilateral nevoid telangiectasia is likely underreported.
The congenital type, though rare, is more common in males than in females. The acquired form is noted more often in females than in males.
Congenital unilateral nevoid telangiectasia may be noted in the neonatal period or soon thereafter. In the acquired form, telangiectases often appear in puberty or in pregnancy, but they may occur at any age.
In acquired unilateral nevoid telangiectasia, the telangiectasias may improve as the estrogen levels decrease, such as following pregnancy or with the discontinuation of oral contraceptives. In other cases of acquired or congenital unilateral nevoid telangiectasia, the lesions persist.
Advise females that the telangiectasias may worsen during pregnancy or with oral contraceptive use.