Monday, April 28

Nevus anemicus - Congenital skin nevus

Nevus anemicus
What is nevus anemicus?
Nevus anemicus is a rare congenital skin anomaly present at birth or in early childhood.
The nevus is more prevalent in women than men. The skin anomaly persists lifelong. It is asymptomatic, neither causing nor exhibiting any symptoms. The macules appear blanched with respect to surrounding skin. The patches are ill-defined having no particular shape or size. Large nevus patches may have small patches of normal skin in between them.

These macules are usually localized appearing mostly on the trunk. A rare case of generalized form had been reported. The anomaly is more prevalent in patients with neurofibromatosis type I. Nevus anemicus was first described by Hans Vorner in the year 1906. He demonstrated that there was reduced dermographism in the nevus when compared to normal surrounding area.

Causes

Nevus anemicus is not a hypopigmentation disorder. In hypopigmentation disorders there is absence or decrease of melanin skin pigment.
  • In this anomaly there is normal pigmentation. The pallor is due to localized decreased blood supply to the skin caused by constriction of blood vessels. In this congenital anomaly of vasculature, there is localized vasoconstriction caused by hypersensitivity to catecholamines.

    Differential diagnosis

    The lesions can be differentiated easily from other hypopigmented lesions with loss of melanin. To differentiate from vitiligo and other hypopigmentation disorders, diascopy, a test for blanchability, is performed on the lesion by applying pressure with a glass slide to observing color changes.
  • On application of pressure, the lesion becomes indistinguishable from the surrounding skin.
  • Under Wood's lamp, unlike fungal infections and hypomelanosis disorders, the macules do not become more emphasized.
  • The macules, unlike the surrounding normal skin, do not show erythematous responses or change color on rubbing, heating or cooling.
  • Histological studies reveal normal pigmentation of the epidermis with no decrease in pigment or melanocytes when compared to the surrounding area.

  • Treatment

    There is no cure for this anomaly. Most of the lesions appear in covered areas of the body. If the macules are present in uncovered area of the skin, for cosmetic purposes camouflaging makeup may be tried.

    Nevus anemicus diagnostic value in Neurofibromatosis type I patients

    nevus anemicus
    nevus anemicus on leg
    Faustine Ferrari et al [1] in their study on diagnosis of Neurofibromatosis type I (NF1), have found that in 72% NF1 cases nevus anemicus was present on the chest and neck. A high frequency of NA in patients with NF1 was observed, especially in children younger than 2 years. They concluded that "NA appear helpful in improving early diagnosis of NF1 in young children and infants."

    Acquired nevus anemicus?

    The anomaly is generally considered congenital and non familial. However, Suhyun Cho et al [2] reported a case of the appearance of pale patch on the neck, one month after a cyst excision in a 53-year-old man. Application of pressure made the patch indistinguishable from the surrounding skin. Rubbing the lesion area made it appear clearly paler than the surrounding reddened area. Application of cold or heat did not induce any change in the lesion. The authors postulate that "the acquired anemic patch that developed after a cyst excision in this case can be explained as a variant of nevus anemicus."
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    References:
    1.Ferrari F, Masurel A, Olivier-Faivre L, Vabres P4. Juvenile xanthogranuloma and nevus anemicus in the diagnosis of neurofibromatosis type 1. JAMA Dermatol. 2014 Jan;150(1):42-6.
    2.Suhyun Cho, Jeong Eun Do, Sang Ho Oh. Acquired Anemic Patch Developed after a Cyst Excision: Is It a Variant of Nevus Anemicus?. Ann Dermatol. Feb 2012; 24(1): 84–86.
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    Image author: Birthmarkshare | License: Public domain
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