Are You Confident of the Diagnosis?
Halo nevi occur when there is an area of depigmentation surrounding a previously existing nevus. The loss of pigmentation generally occurs beyond the borders of the original nevus and may occur over the course of several months or even years. Over time, the original nevus may involute, leaving only the depigmentation with no central pigmented lesion.
Characteristic findings on physical examination
Halo nevi may occur either as solitary lesions or as multiple lesions within the same individual (Figure 1). Lesions often occur on the trunk but can be elsewhere. The preexisting nevus is typically a common acquired nevus, but the halo phenomenon has been reported in conjunction with congenital nevi and Spitz nevi as well.
Expected results of diagnostic studies
Dermatoscopic examination of the central nevus commonly shows a globular and/or homogeneous pattern, which are patterns typically seen in benign melanocytic nevi in children and young adults. Dermatopthology shows nevus cells surrounded by a dense lymphocytic inflitrate.
Who is at Risk for Developing this Disease?
Halo nevi are fairly common and are estimated to occur in approximately 1% of the population. They are often found in a younger population, with a mean age of 15 years. There is no sex predilection. Rarely, the phenomenon can appear to run in families.
What is the Cause of the Disease?
Halo nevi appear to be an immune system response to melanocytes. A mononuclear cell infiltrate can sometimes be seen on microscopic examination in the halo area, and antigen-presenting cells can be present in the regressing nevus. The halo phenomenon is thought to be mediated by CD8+ cytotoxic T lymphocytes, although the exact mechanism and trigger are unclear.
Systemic Implications and Complications
Halo nevi can be associated with other autoimmune disorders, such as vitiligo and Hashimoto thyroiditis. Since halo nevi are relatively common in a young healthy population, the presence of halo nevi in themselves is not generally considered to be an indication for a work-up to detect the presence of additional autoimmune disorders in the absence of appropriate signs or symptoms.
Halo nevi are benign and generally do not require any treatment if the diagnosis is clearcut. It is important for the clinician to consider the possibility that the lesion could represent a partially regressed melanoma. Atypical features such as asymmetry of the lesion or eccentric placement of the pigmented portion should increase suspicion that the lesion may not be a halo nevus, and biopsy could be considered in those cases.
Optimal Therapeutic Approach for this Disease
Although no treatment is necessary for classical halo nevi, any atypical features should warrant a skin biopsy. All patients with a halo nevi should have a full skin examination performed to look for other halo nevi and other pigmented lesions.
No treatment is necessary. Stable halo nevi do not need to be followed by a physician on a regular basis.
Unusual Clinical Scenarios to Consider in Patient Management
The “halo phenomenon” is not limited to melanocytic nevi, but may also be appreciated around other lesions, such as a seborrheic keratosis.
The sudden onset of multiple halo nevi has been rarely associated with melanoma. It is felt that an immune reaction against the melanoma can incite an antimelanocyte response resulting in halo nevi. The melanoma may be ocular in location and a full-skin examination and opthalmologic evaluation should be done. This is especialy important in adults presenting with halo nevi.
What is the Evidence?
Becker, MD, Marcks, KM, Trevaskis, AE, Heffernan, AG, Puchner, G. “Halo nevus of Sutton”. Plast Reconstr Surg. vol. 37. 1966. pp. 413-5. (An early report of the phenomenon.)
Kolm, I, Di Stefani, A, Hofmann-Wellenhof, R, Fink-Puches, R, Wolf, IH, Richtig, E, Smolle, J, Kerl, H, Soyer, HP, Zalaudek, I. “Dermoscopy patterns of halo nevi”. Archiv Dermatol. vol. 142. 2006. pp. 1627-32. (An overview of dermoscopic patterns in this entity.)
Zeff, RA, Freitag, A, Grin, CM, Grant-Kels, JM. “The immune response in halo nevi”. J Am Acad Dermatol. vol. 37. 1997. pp. 620-4. (An examination of the evidence in support of the halo phenomenon being a T-cell-mediated event.)
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