By Gary M. White, MD
The nevus anemicus is a white, congenital lesion, relatively devoid of blood in which the skin's blood vessels are permanently vasoconstricted. The defect appears to be a result of increased local sensitivity to catecholamines. If the skin is grafted to another site, it retains its vasoconstriction, thus implying that the blood vessels themselves have an increased sensitivity to catecholamines as opposed to increased sympathetic stimulation [Dermatology 1999;199;327].
A pale, hypopigmented and sharply demarcated, irregular patch is seen. The lesion occurs most commonly on the torso. The edge can be obliterated for a few seconds by compressing the skin with one's hand, thus verifying that it is blood and not melanin that causes the difference in color. Rubbing the edge will also accentuate the lesion as the surrounding skin becomes hyperemic.
Nevus anemicus appears more common in patients with neurofibromatosis. In one study, 51% of patients with NF-1 had a nevus anemicus compared with only 2% of control subjects [JAAD 2013;69;768–775]. It may also be more common in tuberous sclerosis.
Phakomatosis pigmentovascularis IIb is NA along with nevus flammeus and a mongolian spot.
No treatment is usually needed. For the rare lesion on the face, makeup may be necessary.
Pressing on the edge obliterates it.
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