Diagnosis: Nevus anemicus

The patient was diagnosed with nevus anemicus, a congenital anomaly characterized by localized pallor in a single well-defined but irregularly shaped patch, usually occurring on the trunk. The macule appears early in life and occurs more commonly in women. Because the lesion is asymptomatic and frequently subtle in appearance, it may go unnoticed by the patient or be found incidentally on skin examination.

The diagnosis of nevus anemicus is readily made via diascopy in which firm pressing of a glass microscope slide causes blanching of erythematous skin. When diascopy is applied to the edge of a nevus anemicus, the border between the pale anomalous patch and the surrounding skin is obliterated. In addition, application of heat or gentle friction to the area will cause the surrounding skin to flush due to hyperemia while the anomalous skin will remain pale, its border accentuated by the surrounding erythema.

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Described as a “pharmacologic nevus,” nevus anemicus is thought to be due to focal areas of abnormal vasoconstriction resulting from hypersensitivity to circulating catecholamines. Injection of vasodilators, such as bradykinin and serotonin, cause erythema of surrounding skin but do not affect the pallor of a nevus anemicus. The pallor is abolished, however, by local sympathetic blockade with lidocaine, rendering the lesion indistinguishable from surrounding skin.1 

Erythema was also produced by local injection of phentolamine, an alpha-adrenergic blocking agent.2 Further studies revealed that skin plugs transplanted from a nevus anemicus to non-lesional skin retained the characteristics of the nevus anemicus, demonstrating donor dominance of the nevus anemicus phenotype.2 Histologic evaluation of the nevus anemicus showed no abnormal findings. This evidence suggests that the relative pallor of a nevus anemicus is due to local hypersensitivity to circulating catecholamines rather than local excess of adrenergic activity.

Differential diagnoses of nevus anemicus include disorders of hypopigmentation, e.g., vitiligo; nevus depigmentosus; tinea versicolor; and leprosy. 

Our patient’s lesion was not treated. 

Dr. Vandergriff is a dermatology resident at The University of Texas Southwestern Medical Center in Dallas. Dr. Garman has a private dermatology practice in Houston, where Dr. Hsu is professor of dermatology at Baylor College of Medicine.

1. Greaves MW, Birkett D, Johnson C. Nevus anemicus: a unique catecholamine-dependent nevus. Arch Dermatol. 1970;102:172-176.
2. Daniel RH, Hubler WR, Wolf JE, Holder WR. Nevus anemicus. Donor-dominant defect. Arch Dermatol. 1977;113:53-56.