Efficacy of 308-nm Monochromatic Excimer Light in the Management of Halo Nevi: An Open-Label, Pilot Study

INTRODUCTION

Sutton[1] described halo nevi (HNs) as leukoderma acquisita centrifugum in1916. These are common benign melanocytic nevi in which an inflammatory infiltrate develops that result in surrounding zone of depigmentation, giving rise to a halo around the melanocytic nevus.[1] HN affects 1% of the population with no sex predilection.[2] The association between vitiligo and halo nevi is long been debated with some authors consider halo nevi as one end of the spectrum of vitiligo,[3] whereas others consider them as two different entities.[456] HN can be traditionally associated with dysplastic nevus[7] and malignant melanoma.[8] Either of these conditions are extremely rare in Indian subcontinent wherein benign HN is usually encountered. Hypo- or depigmented macules on body impart a lot of psychosocial disturbances in patients with pigmented skin. Various treatment modalities ranging from no intervention[9] to topical tacrolimus,[10] surgical excision of nevus,[11] and excimer laser[1213] are reported in the literature. Monochromatic excimer light (MEL) has a similar mechanism of action to the excimer laser.[14] We decided to use MEL on HN.

MATERIALS AND METHODS

After obtaining ethical clearance and informed written consent, a total of 29 consecutive patients with HN were included in the study. Site and size of HN were noted and respective demographic data were collected. Patients with generalized vitiligo, those treated with phototherapy in the past 3 months and those with a history of immunosuppressive or photosensitizing agents were excluded from the study. A dermoscopic examination of nevus was carried out in all patients to rule out atypical patterns.

RESULTS

A total of 29 patients with 10 males and 19 females (male to female ratio of 1:1.9) completed the study. The age of onset of HN ranged from 5 to 47 years and the mean age of the patients was 23 years. Patient characteristics, the result obtained, and doses used are summarized in Table 1.

The percentage of repigmentation in different age groups and gender is shown in Tables 2 and 3, respectively. HN was distributed all over the body, 5 (17.2%) patients had it on the face, 6 (20.7%) on the neck, 4 (13.7%) each on the chest, trunk, and back, and 5 (17.2%) and 1 (3.4%) on the lower and upper extremities, respectively. The number of sessions to achieve satisfactory response ranged from 5 to 39 sessions, with an average number of sessions of 18.3. The frequency of repigmentation in different body sites is shown in Table 4. Maximum fluence ranged from 400 to 2800 mJ/cm² to attain repigmentation. The average fluence used in the study ranged from 400 to 1671 mJ/cm² with a mean fluence of 748 mJ/cm².

An outstanding response was noticed in 14 (48.2%) patients [Figures 1–4], whereas 6 (20.6%) patients showed excellent improvement [Figures 5 and 6]. Very good and partial improvement was observed in 6 (20.6%) patients and 1 (3.4%) patient, respectively [Figure 7]. Only 2 (6.8%) patients showed no response after 10 consecutive sessions and declared the treatment as failure. Dermoscopy showed diffuse structureless area at the periphery with reticular pigment network in the center. After treatment, it showed an increased amount of melanin in the nevus area and pockets of reticular pigment network in the white area [Figure 8]. The lesion on the face and neck responded fast, and lesions on the extremities took relatively long time to respond. But no statistically significant difference was observed between the lesion location and the outcome of the treatment by analysis of variance, which is shown in Table 5.

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Figure 1

Clinical image of halo nevus on the face showing outstanding improvement after MEL treatment

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Figure 2

Clinical image of halo nevus on the face showing outstanding improvement after MEL treatment

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Figure 3

Clinical image of halo nevus on the back showing outstanding improvement after MEL treatment

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Figure 4

Clinical image of halo nevus on the chest showing outstanding improvement after MEL treatment

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Figure 5

Clinical image of halo nevus on the thigh showing excellent improvement after MEL treatment

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Figure 6

Clinical image of halo nevus on the back showing outstanding improvement after MEL treatment

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Figure 7

Clinical image of halo nevus on the upper leg showing very good improvement after MEL treatment

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Figure 8

(A) Dermoscopy of halo nevus showing pigment network (yellow star) in the center surrounded by diffuse structureless white areas (black stars) (left panel). (B) After treatment, faint pigment network (black arrows) is well appreciated in the white structureless area and also note the increased melanin amount in the pigment network (blue star) (right panel)

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All patients tolerated the procedure well. Only one patient with HN on the chest developed intense erythema and blistering at the site, which resolved on its own. This particular lesion did not respond to treatment. Two patients developed vitiligo in the perilesional skin during the course of treatment but both of them responded to MEL with complete repigmentation. We did not contemplate perilesional hyperpigmentation as a complication rather it was considered as the normal outcome of treatment as the patients in this study were of skin type 4 and 5. However, it was minimized by using silicone stencils and interestingly, it resolved in all patients after discontinuation of MEL.

DISCUSSION

HN is found most commonly in children. The average age of onset is 15 years. In our study, it was 23 years. There is no predilection for sex or race.[2] In our study, female outnumbered male by 2:1 ratio. This can be attributed to greater awareness in the female subjects because of social stigma.

HNs can develop anywhere on the body but are seen most frequently on the trunk.[15] The neck is the most common site involved in our study followed by the face and lower extremity.

The treatment of HN is controversial. There are reports for spontaneous resolution of halo nevi with the disappearance of nevus and repigmentation of halo.[9] The appearance of halo represents the onset of nevus regression and disappearance of nevus leaving behind a depigmented halo. Eventually, the halo gets repigmented spontaneously.[1516] Aouthmany et al.[17] reported the average duration for complete resolution of the halo as 7.8 years. They also reported that 51% of HN showed no change after an average of 4.2 years, and 78% of HN failed to resolve during an average follow-up of 5.6 years.[17] Such a long duration for spontaneous resolution is unacceptable in our patients.

There are not many reports on the treatment of HN. Hossain[10] treated two cases of benign halo nevi with topical tacrolimus ointment. Wang et al.[11] treated HN by complete excision. They also reported repigmentation of associated vitiligo following excision. Excision of HN is not always possible because of the size and location. The resulting scar may be unacceptable to many of the patients, and the frequency of achieving the regression of depigmented halo after excision is lesser and sometimes it takes place after many years.[11]

Excimer lasers are sometimes called as “exciplex” lasers, which are pulsed gas lasers typically emitting ultraviolet light. The term “excimer” is used as the short form of “excited dimer.” It uses noble gas and halide molecules. The 308-nm MEL particularly uses xenon as a noble gas and chloride as a halide molecule.

MEL has a similar mechanism of action as that of a laser.[14] It emits monochromatic ultraviolet light of 308-nm wavelength, which unlike laser is non-collimated and noncoherent. It causes T cell apoptosis resulting in immunosuppression. It also results in DNA damage and stimulates melanocytic-stimulating hormone and melanocytic proliferation. These effects eventually bring in the repigmentation in the depigmented areas of vitiligo or HN.[1819] Localized vitiligo responded well with MEL in many studies and the most effective result was observed in the lesions on the face and neck.[11] Chimento et al.[20] in a pilot study treated 10 patients of stable vitiligo with ME and concluded that 308-nm MEL is a safe and effective therapeutic option in patients with stable vitiligo in skin types 3 to 6. Nisticò et al.[21] studied 53 patients of vitiligo and concluded that 308-nm MEL alone or in combination with 0.1% tacrolimus is effective in the treatment of vitiligo.

Mulekar et al.[12] treated four cases of HN on the face with an excimer laser. They reported 100% repigmentation in two cases and 80% repigmentation in the remaining two cases. They also reported retention of pigment at 18 months follow-up without any changes suggestive of melanoma.[12]

On the basis of this report and reports of successful treatment of vitiligo with MEL,[22] we decided to treat HN with MEL. In this study, patients with lesions affecting the facial and non-facial areas were selected. All patients showed improvement ranging from outstanding to good except two patients in whom no improvement was reported even after 10 consecutive sessions. No malignant changes were noticed in this study following MEL treatment. No statistically significant variation was reported in the treatment outcome based on the location of the lesion. However, lesions located on the face and neck responded faster as compared to that on the other areas. No studies are available to compare this entity in the literature. Nevertheless, in vitiligo, MEL produces better results in the facial and neck lesions as compared to lesions affecting other areas of the body.[23]

Association of melanoma with HN or development of melanoma following MEL treatment of HN is a great concern. There are reports to support the occurrence of melanoma after ablative lasers treatment.[24] A large systematic review by Eggen et al.[25] found no evidence of malignant transformation of congenital melanocytic nevus treated with lasers. In a doubtful case, dermoscopy or biopsy should be carried out to rule out melanoma. Having said this, it is also important to remember that incidence of melanoma in skin types 4, 5, and 6 is very low. A study by Weyant et al.[26] also confirmed that HN arise from a variety of histologic types of nevi, most of which are not dysplastic. Kolm et al.[27] examined 138 HN in 87 patients with dermoscopy and found that HN exhibits the characteristic dermoscopic feature of benign melanocytic nevi. Thus, we believe that MEL in HN is a good therapeutic option because repigmentation occurs with a rapidity, which is also cosmetically acceptable by the patients. In this study, repigmentation was satisfactory in most patients. Although no significant difference in the treatment outcome between the sites and size of HN was observed, lesions on the face and neck achieved faster repigmentation as compared to lesions present in other areas.

CONCLUSION

HN causes apprehension in the Indian population because of the social stigma associated with depigmented or hypopigmented patches on the body. Mere observation and carrying out simple follow-ups in treatment protocol are not sufficient. Hence HN should be treated. MEL is a noninvasive procedure, which results in excellent repigmentation of HN without scarring.