Atypical Presentation of Halo Nevus over Eyelid with Poliosis: A Dermatoscopic Perspective.

Halo nevus (HN) is benign skin condition with a central melanocytic nevus, surrounded by an area or halo of depigmentation. It is the result of immunological response of the body toward the nevus, which destroys the melanocytes in surrounding skin, leading to the depigmented halo. An increased frequency of HN in patients with vitiligo is observed. It is more commonly seen in children or young adults of either sex, particularly on the trunk, less commonly on the face, neck, and limbs. We present a rare case of HN which was present on the lower eyelid associated with poliosis, diagnosed with dermatoscopy. Copyright:

INTRODUCTION

Halo nevi (HN) or leukoderma acquisitum centrifugum is characterized by a ring of depigmentation appearing around acquired or congenital melanocytic nevi. It usually appears in childhood and early adolescence with no sex predilection.[1] HNs are usually single but may be multiple and develop anywhere on the body but are seen most frequently on the trunk and clinically, present with tan, pink, or brown uniformly colored, round or oval nevi in center with peripheral margins of hypo- or depigmentation. The width of the halo is variable but is generally of uniform radial distance from the central nevus. Self-limited immunological response against the melanocytic cells of the nevus leading to nevus cell destruction in the normal skin or within the melanocytic nevus is the proposed pathophysiology of the halo phenomenon.[2] It can be rarely associated with poliosis which is a localized area of hypopigmented hair caused by a reduction or absence of melanin in a group of follicles. No treatment is required as it has a tendency to get flattened and disappear completely over a period of time.

CASE REPORT

A 26-year-old female came to skin OPD with an asymptomatic brownish lesion over left lower eyelid for the past 6 months, with whitish discoloration of hair limited to that area. She complained that after 2 months of appearance of lesion, there was loss of few eyelashes and then for 1 month, surrounding skin and eyelashes turned whitish. Cutaneous examination showed a single brownish-black papule of size approximately 0.5 cm × 0.5 cm over left lower eyelid, between the medial one-third and lateral two-thirds of the eyelid [Figure 1]. There was depigmentation of surrounding skin about 0.5 cm surrounding the nevus with leukotrichia. There were no depigmented lesions elsewhere on the body suggesting vitiligo. Her vision was not impaired due to the lesion and her visual acuity was normal. Rest of the cutaneous and systemic examination was normal. There was no associated family history of similar lesions or any autoimmune conditions. Dermatoscopy done with handheld LED Illuco dermoscope IDS-1100 having polarized light illumination having ×10 magnification showed bluish pepper-like granules, globules, surrounding depigmentation and leukotrichia [Figure 2]. Diagnosis of HN developing surrounding acquired melanocytic nevus was made. Patient's main concern was cosmetic, so melanocytic nevus was excised through electrocautery. The depigmented patch persisted and is expected to fade with time [Figure 3].

Figure 1

Single brownish-black papule of size approximately 0.5 cm × 0.5 cm present over left lower eyelid with surrounding depigmentation

Figure 2

Dermatoscopy showed bluish pepper-like granules (white arrow), globules (green arrow), surrounding depigmentation (red arrow), and leukotrichia (black arrow)

Figure 3

Melanocytic nevus excised through electrocautery

DISCUSSION

The HN phenomenon is relatively common acquired hypomelanosis around pre-existing nevi. The associated nevi most commonly are acquired melanocytic which can be a junctional, dermal, or compound nevus.[3]

Its etiology is unknown, but it is believed that the onset of a HN may be triggered by sunburn or local trauma, which causes the nevus to be recognized by the immune system as foreign, resulting in an immune response against the existing aggregates of melanocytic nevus cells.[4] The reaction also affects the normal skin around the nevus, which too has melanocytes in it, causing depigmentation. The infiltrating cells are predominantly T-lymphocytes and among them, cytotoxic (CD8) lymphocytes outnumber helper (CD4) lymphocytes by a ratio of approximately 4:1 and also macrophages. A recent study demonstrates complete absence of immune cells in HN specimens and proposed a theory based on vascular origin where vascular endothelial cells were found to be replacing melanocytes. In another more recent study, tumor necrosis factor-related apoptosis-inducing ligand has been suggested as a plausible causative factor for both HN and vitiligo.[5]

The incidence of HN in the population is estimated to be 1%. It undergoes specific changes over the time through 4 stages:[6]

Stage1 – Central nevus remains brown in color

Stage 2 – Pigment disappears leading to a pink-colored papule

Stage3 – The central papule may disappear, leading to a circular area of depigmentation

Stage 4 – The depigmented area may repigment with the time, leaving no trace of its existence.

The diagnosis of HN is basically clinical, but dermoscopic patterns such as uniform, globular, and structureless areas have been described.[7]

Dermoscopy of HN is characterized by the occurrence of the globular pattern with blue pepper-like granules and/or white-scar areas.[8] Our patient had similar findings. On histological examination, there is proliferation of melanocytes as nest and solitary units at the dermoepidermal junction and in the dermis toward the center of the lesion. Furthermore, there is dense lymphocytic infiltrate extending from the dermoepidermal junction to the base of the lesion, with absent melanocytes and pigmentation at the periphery of the lesion.[9] We did not do biopsy as patient was not willing for the same.

Up to 26% of patients with HN have vitiligo. Multiple HN, the presence of Koebner phenomenon, and a family history of vitiligo have been identified as possibly increasing the risk of vitiligo in patients with HN.[10] It is usually a benign condition but may turn into malignancy, the risk being 5%–10% in a giant melanocytic nevus. Our patient did not have family history of vitiligo.

Poliosis, that is white discoloration of hair with HN, is a rare phenomenon, which was seen in our patient. It is due to predilection of melanin-rich hair follicles for immunologic reactivity or due to inflammation resulted from an exaggerated cell-mediated immune response to the nevus. Acquired poliosis of the eyelashes has been described in several ophthalmic conditions, including blepharitis, sarcoidosis, sympathetic ophthalmia, herpes zoster, Vogt-Koyanagi-Harada syndrome, vitiligo, tuberous sclerosis, postirradiation, and with topical administration of prostaglandin F2 analogs.[11]

A case of poliosis over eyelids was diagnosed as a presenting sign of the halo phenomenon in the regressive stage of a melanocytic nevus[6] like our case, thus our's is second such case in literature of HN with poliosis over eyelid, and first with dermatoscopic changes.

The differential diagnosis of HN includes recurrent nevus within a scar, melanoma with halo phenomenon, solar lentigo, or seborrhoeic keratosis undergoing regression.

Patients with halo melanocytic nevi usually seek medical attention when their pigmented lesions develop a rim of depigmentation. It may remain stable for years and it is possible that complete repigmentation may occur later in life; thus, periodic follow-up to observe for any malignant change is recommended.

CONCLUSION

A case of HN in a 26-year-old female, over a rare site (left lower eyelid) accompanied with leukotrichia, is presented. It is important to counsel patient regarding the possibility of spontaneous repigmentation in cases of HN and regular monitoring for associated vitiligo and possible malignant change.

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Conflicts of interest

There are no conflicts of interest.