​Dermatology - Halo Nevomelanocytic Nevus

​Dermatology - Halo Nevomelanocytic Nevus
Halo nevI are characterized by the presence of moles surrounded by a ring of leukoderma or loss of pigmentation. This occurs due to an autoimmune process that causes the death of nevus cells and melanocytes in the surrounding skin. Halo nevi are found in about 1% of the population. The presence of a white halo signifies regression, and halo nevi typically experience spontaneous involution.

The process consists of three stages: (1) the formation of a white halo around an existing NMN, which may be preceded by a faint redness, lasting for several months; (2) the gradual elimination of the NMN over a period of months to years; and (3) the subsequent repigmentation of the halo, also taking months to years.
Abnormalities
Papular brown moles, which are smaller than 5 mm, exhibit a distinct oval or round halo with well-defined hypomelanosis.
The diagnosis is based on clinical evaluation, and "halo" depigmentation can be observed surrounding several types of skin lesions, such as blue nevus, congenital melanocytic nevi, Spitz nevi, verruca plana, primary melanoma, melanoma metastases, dermatofibroma, and neurofibroma.


To exclude melanoma, it is important to consider abnormal clinical characteristics such as asymmetry, irregular borders, variegation of color, big diameter, or growth in size of the nevus.