Unilateral nevoid telangiectasia (UNT), also known as unilateral dermatomal superficial telangiectasia, is a cutaneous condition characterized by telangiectasias present in a dermatomal or Blaschkoid distribution. UNT most commonly involves the C3-C4 or trigeminal dermatomal regions, and it may be congenital or acquired. The congenital form is less common and has a male predominance, whereas the acquired form is more common and has a female predominance. The condition is asymptomatic.

Acquired UNT typically occurs in conjunction with physiologic states of elevated estrogen levels, such as hormonal therapy, puberty, and pregnancy in women, and adrenarche in men. This condition has also been reported to develop in pathologic states of elevated estrogen, such as chronic hepatic disease and alcohol use disorder. However, there are reports of acquired UNT occurring in both children and adults in the setting of normal serum estrogen levels and normal liver function studies.

The etiology of UNT is unknown; the current theory is that UNT occurs in a circumstance of relative estrogen excess. This relative estrogen excess subsequently unmasks a localized increase in estrogen receptors caused by chromosomal mosaicism. Other speculated mechanisms for the development of UNT include neural alterations, hemodynamic disturbances, abnormalities in perivascular connective tissue, and angiogenic factors.