1. What is the most likely diagnosis (Figure 1)?
a. Dysplastic nevus
b. Halo nevus
c. Nevus depigmentosus
d. Spitz nevus
2. A child developed a patch of white hair as shown in Figure 2. What is the
most likely diagnosis?
a. Waardenburg syndrome
b. Traumatic pigment loss
c. Halo nevus
d. Premature canities
Answers: 1b, 2c
Discussion:
Halo nevi are common lesions present in
approximately 1% of children and young adults.[1] Halo nevi present clinically
as a centrally placed brown, black or pink papule, surrounded by a halo of
depigmentation. The halo of depigmentation varies widely in size, but most often
measures from 1 to 5 mm around the central nevus. White hair can also be noted
within the halo. Many types of nevi can be associated with this halo phenomenon,
including acquired nevi, congenital nevi, blue nevi, Spitz nevi, and rarely in
children, melanoma. Although the etiology of the halo is unknown, its
development appears to be related to an immune response against
melanocytes.[2]
Several diseases and syndromes have been
associated with halo nevi, including vitiligo, poliosis, Vogt-Koyanagi-Harada
syndrome, pernicious anemia, and a personal or family history of melanoma.[3]
The strongest association is with vitiligo, which occurs in 18%–26% of
patients.[3] The presence of halo nevi in pediatric patients may herald the
development of vitiligo and a thorough exam should be performed for this
possibility. In addition, a complete history and physical examination are most
often sufficient to reveal other conditions.
Halo nevi in children and adolescents typically
follow a benign course with loss of the original pigmented lesion followed by
repigmentation of the halo over several months to years. The halo phenomenon
appearing around a melanoma occurs in adults, but is exceedingly rare in
children and adolescents. Of note, no pediatric dermatologist in a recent survey
has ever seen a typical halo nevus develop into a melanoma.[4] Hence, the
development of a depigmented halo around an otherwise benign appearing nevus on
a child should not be cause for concern or reflexively lead to a
biopsy.
It is difficult to
apply the "ABCD" diagnostic criteria for melanoma to halo nevi. These criteria
include Asymmetry (each half of the nevus does not match the other in
shape), Border irregularity (notching or scalloping in the border), Color variegation
(the nevus contains multiple colors andshades),andDiameter(>6 mm).[3] The immunologic destruction of
melanocytes and nevus cells may cause the central nevus to appear irregularly
pigmented. Despite these expected changes, atypical features should prompt
consideration for an excisional biopsy. Of note, the surrounding rim of
depigmentation does not need to be included within the biopsy.
Atypical features include asymmetric
depigmentation or a central nevus that displays atypia as defined by the "ABCD"
diagnostic criteria for melanoma. Other concerning signs include a rapid
enlargement of the central nevus, ulceration, or bleeding.
As with any patient with pigmented skin lesions,
all patients with halo nevi should have a full-body skin examination, including
the mucous membranes. Patients should be followed periodically for the
development of atypical nevi, melanoma, and vitiligo. In addition, the same
general guidance should be given to patients with halo nevi as with any patient
with pigmented nevi. Patients and their parents should be advised on minimizing
UVR (ultraviolet radiation) overexposure by avoiding outdoor activities when
ultraviolet exposure is most intense (10 am to 2 pm); wearing sun-protective
clothing; and applying ample sun screen with appropriate UVA and UVB protection.
Patients and their parents should also be taught the basic signs for concerning
nevi (ie, the "ABCD" diagnostic criteria) and instructed on proper periodic
self-skin exams.
REFERENCES
[1.] Larsson P,
Liden S. Prevalence of skin diseases among adolescents 12-16 years of age. Acta
Derm Venereol (Stockh) 1980;60:415-423.
[2.] Zeff RA,
Freitag A, Grin CM, Grant-Kels JM. The immune response in halo nevi. J Am Acad
Dermatol 1997;37(4):620-624.
[3.] Grichnik
JM, Rhodes AR,
Sober AJ. Melanocytic tumors. In: Fitzpatrick's Dermatology in General Medicine.
7th ed. New
York: McGraw-Hill;
2008.
[4.] Lai CH,
Lockhart S, Mallory SB. Typical halo nevi in childhood: Is a biopsy necessary? J
Pediatr 2001;138:283-284. | 
