Introduction
Nevus anemicus typically manifests as a single spot on the skin with no additional symptoms. This condition is believed to be brought on by the skin's blood vessels becoming permanently constricted and losing pigment due to being overly sensitive to chemicals like epinephrine and norepinephrine.
According to dermatology research, nevus anemicus is present in one to two percent of control groups. However, the prevalence may be higher since it can be challenging to identify the condition's subtle symptoms, particularly in people with lighter skin. Additionally, females are slightly more likely than males to develop nevus anemicus.
What Is Nevus Anemicus?
Nevus anemicus is a rare capillary vascular anomaly that manifests as a light-colored patch on the skin at birth. This happens as a result of increased catecholamine sensitivity, which causes the blood vessels in that area to constrict. Vorner first recognized this uncommon condition back in 1906.
What Causes Nevus Anemicus?
Nevus anemicus typically manifests as a single skin patch without other associated symptoms. The hypopigmented patches seen in nevus anemicus are caused by vasoconstriction of the blood vessels. These blood vessels are highly sensitive to circulating catecholamines like noradrenaline and adrenaline, which interact with alpha-adrenergic receptors and cause constriction. Nevus anemicus has also been referred to as a "pharmacologic nevus" because of its sensitivity to catecholamines.
The disorder is considered a mosaic disorder brought on by mutations following fertilization. Interestingly, nevus anemicus appears resistant to dermatophyte infections like Trichophyton rubrum. This may be because the affected skin has less blood flow and a lower core temperature. Because they lack expression of specific molecules which attract T lymphocytes responsible for the inflammation of contact dermatitis, nevus anemicus lesions may also be spared by generalized contact dermatitis. These proteins include HLA-DR, epidermal intercellular adhesion molecule-1 (ICAM-1), and endothelial E-selectin.
Whether isolated nevus anemicus lesions have a genetic component is not yet known. However, some genetic syndromes have been linked to this condition, including neurofibromatosis type I and types II to IV of phakomatosis pigmentovascularis. All forms of phakomatosis pigmentovascularis have the distinctive port wine stain, while types II and IV also have Mongolian spots, nevus spilus, and type III only has nevus spilus.
Nevus anemicus tends to appear earlier (around ten years of age) in patients with neurofibromatosis type 1 than in those without (around 17 years of age), though it does not increase the likelihood of other neurofibromatosis type 1-related conditions like optic gliomas.
Legius syndrome does not have nevus anemicus, even though it resembles neurofibromatosis type 1 due to the presence of cafe-au-lait (coffee-milk like) macules and intertriginous freckling. Rare reports have also linked nevus anemicus to Becker nevus and telangiectatic nevus, exhibiting abnormal vasodilation.
What Are the Clinical Features of Nevus Anemicus?
Nevus anemicus is characterized by hypopigmented patches with a clear border that appears at birth. These patches tend to be asymptomatic and can be found on the upper trunk, but they can also be found on the face and limbs. Nevus anemicus does not affect hair distribution, sweat production, or skin sensation. It does not turn erythematous on rubbing the lesion.
These patches are typically 5 to 10 centimeters in size. Still, in certain instances, they can be large enough to cover significant areas of the trunk, referred to as "giant nevus anemicus." These patches may contain areas of normal skin within the lesion and smaller hypopigmented patches around the lesion. Lesions can also appear as linear or coalescing macules that resemble grape clusters.
How Is Nevus Anemicus Diagnosed?
Since there are no definitive histopathologic features that distinguish nevus anemicus from other skin conditions, the diagnosis is heavily reliant on the patient's medical history and physical examination. It is important to note that nevus anemicus appears at birth, whereas other depigmented conditions, such as vitiligo (chronic skin condition characterized by loss of skin color), appear later in life.
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One feature of nevus anemicus is the absence of reactive erythema in response to stimuli such as heat, cold, or trauma. This can be tested by rubbing the lesion and surrounding skin or by changing the temperature, which causes the surrounding skin to turn red while the nevus anemicus lesion persists as pale.
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Diascopy is another diagnostic technique that involves pressing a glass slide against the lesion's border, causing the lesion to blend in with the surrounding skin.
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The Wood's lamp, which produces UV (ultraviolet) light with a wavelength of 365 nanometers, can help diagnose skin conditions. It does not improve the hypopigmentation of nevus anemicus, but it improves the hypopigmentation and depigmentation of nevus depigmentosus and vitiligo.
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A skin biopsy can be performed to rule out other hypopigmented or depigmented lesions that would show normal skin, such as vitiligo.
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Electron microscopy of nevus anemicus reveals normal findings, whereas nevus depigmentosus reveals normal melanocyte numbers but reduced melanization with melanosome aggregation in melanocytes.
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If tinea versicolor is suspected, lesional skin should be examined with potassium hydroxide (KOH), which reveals the spaghetti and meatballs appearance of Malassezia furfur hyphae and spores.
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It is important to differentiate nevus depigmentosus from nevus anemicus during clinical examination. Redness occurs after rubbing the skin in nevus depigmentosus. However, erythema does not occur in nevus anemicus.
How Is Nevus Anemicus Treated?
Once diagnosed, nevus anemicus does not need any therapy. Nevus anemicus does not often require treatment because it is asymptomatic and causes no functional impairment. Patients with nevus anemicus who feel self-conscious about their cosmetic appearance, on the other hand, may benefit from camouflage makeup. Camouflage makeup can assist in blending the lesion with the surrounding skin, creating the illusion of a more even skin tone. It is a non-invasive and safe method for improving the appearance of nevus anemicus. Use of good quality cosmetic products can help to camouflage this cutaneous condition on the face.
Conclusion
Nevus anemicus is an uncommon congenital skin condition that causes hypopigmented patches with a distinct border that appears at birth. A thorough history and physical examination, as well as diagnostic tools such as a Wood's lamp, can help to determine the presence of nevus anemicus. While the condition is asymptomatic and does not usually necessitate treatment, patients may have cosmetic concerns due to the appearance of the lesions. Camouflage makeup can help patients bothered by the cosmetic appearance of their lesions.
