By Kristy Fleming, MDAn otherwise healthy 33-year-old woman presented for a routine annual full-body skin exam. She was concerned about a white area on her mid-upper back. Given the location of the lesion, the patient was not able to see it very well. She was unsure how long the lesion had been present or if it had changed in size, shape or color. She denied pain or pruritus and had no similar lesions elsewhere on her body. Exam revealed a cluster of irregularly shaped hypopigmented macules without induration, scale or surface change. When pressed firmly with a glass microscope slide, the macules quickly faded and the patient’s normal skin pigmentation appeared under the slide. The hypopigmented macules returned when the slide was released. What’s your diagnosis? Submit your answer, and then read the full explanation below. If you like this activity or have a suggestion, tell us about it in the comment box at the bottom of the page.
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Nevus anemicus is a congenital vascular anomaly that may be noted at birth or during childhood, but is often overlooked and discovered during routine skin exams. The lesions are asymptomatic and entirely benign. The exact prevalence is unknown, but nevus anemicus is fairly common.
Nevus anemicus presents as hypopigmented macules, varying in size and shape.1 The lesions are well demarcated, but often have a jagged, irregular border. Macules are most commonly located on the patient’s trunk.
Underlying blood vessels with a heightened sensitivity to endogenous catecholamines make up nevus anemicus lesions.2 This sensitivity results in a chronic state of localized vasoconstriction and explains the hypopigmentation.
Studies indicate nevus anemicus is a donor-dominant condition, meaning that normal skin transplanted within the lesion will maintain the characteristics of the donor site.3
Nevus anemicus presents similar to many hypopigmentation or depigmentation cutaneous conditions, and a number of diagnostic tools are available to quickly eliminate differential diagnoses while the patient is in the office.
Unlike vitiligo or ash-leaf macules, there is a normal amount of melanin in nevus anemicus. As a result, Wood’s light will not accentuate the lesion.2
Diascopy simulates the vasoconstriction present with nevus anemicus, causing the surrounding skin to blanch and making the lesion indistinguishable. Conversely, applying heat or cold to the area will cause erythema on surrounding skin without producing an effect on the lesion, which accentuates the contrast between the two and makes the nevus anemicus lesions appear more prominent.1
Triple response of Lewis, a triphasic skin reaction to being stroked firmly with an instrument, is another useful diagnostic tool. This reaction initially consists of a red line that develops at the site of contact due to histamine release. A flare then develops around the red line, and a wheal forms as a result of local edema. In patients with nevus anemicus, the flare response is absent but will be present in the adjacent skin. 2
There are no characteristic histologic features with nevus anemicus, so a skin biopsy will appear identical to normal skin.1
Fortunately, nevus anemicus is a completely benign condition. Patients can be reassured that no treatment is required, but that lesions will likely persist unchanged throughout life.
Patients who are displeased with the cosmetic appearance can be counseled to cover the area with camouflage makeup.
1. Bolognia J, Jorizzo JL, Rapini RL. Dermatology, 2nd Ed. Elsevier; 2008: 624.
2. James WD, Berger TG, Elston DM. Andrew’s Diseases of the Skin Clinical Dermatology, 10th ed. Saunders Elsevier; 2006: 582.
3. Daniel RH, Hubler WR, Wolf JE et al. Arch Dermatol. 1977;113: 53-56.