Epidermal grafting for leukoderma resulting from 1064‐nm quality‐switched neodymium‐doped yttrium aluminium garnet laser toning

Abstract

Leukoderma secondary to Q‐switched 1064‐nm neodymium‐doped yttrium aluminium garnet laser is usually refractory to treatment. The pathogenesis was cumulative phototoxic damage to melanocytes and eventually resulted in melanocytopenia. Wood's light or UV imaging can help observe early leukoderma before it becomes apparent clinically and determine the degree of melanocytopenia before conducting a biopsy. NB‐UVB phototherapy and 308‐nm excimer laser can potentially worsen the pre‐existing melasma lesions and may not be effective if the lesions have already become melanocytopenic. Epidermal grafting can replenish the hypopigmented area with melanocytes without worsening melasma.

1. INTRODUCTION

Since 2007, 1064‐nm Q‐switched neodymium‐doped yttrium aluminium garnet (QS Nd‐YAG) laser toning with low fluence, large spot size, and multiple passes has been commonly used for non‐ablative skin rejuvenation and the treatment of melasma in Asian countries.1 It can temporarily improve melasma lesions with minimal downtime. However, complications include leukoderma and mottled hypopigmentation, and the incidence has been reported to be 0%–16.8%.1

Leukoderma secondary to laser toning has been reported to be a melanocytopenic disorder according to biopsy results and is refractory to treatment.2 Narrow‐bandUVB and a 308‐nm excimer laser have gained variable success but can aggravate the pre‐existing melasma lesions.3 Here, we report a case using epidermal grafting rather than phototherapy to treat leukoderma caused by repeated QS Nd‐YAG laser toning.

2. CASE PRESENTATION

A 44‐year‐old Taiwanese woman presented with multifocal prominent hypopigmented macules over a background of brown patches on her cheeks bilaterally. Melasma on her forehead and bilateral cheeks was treated fortnightly with a 1064‐nm QS Nd:YAG laser (MedLite C6TM; Hoya ConBio Inc., Fremont, California, unknown parameters) at a local clinic. After the 10th laser toning, punctate hypopigmentation spots appeared first on her forehead, bilaterally. However, the laser toning sessions were still ongoing, and hypopigmented spots appeared on her cheeks and gradually enlarged. She stopped the treatment after the 16th session; however, the hypopigmented skin still lasted for 1 year. She presented to our clinic, and the lesions were accentuated under Wood's lamp (Figure 1A,B). To decrease the contrast between the hyper‐ and hypopigmented areas, we offered three low‐fluence QS Nd YAG laser treatments, set at 1.6 J/cm² with a 7‐mm spot size without overlapping, to reduce the hypopigmented areas at a 2‐month interval and oral tranexamic acid at a dose of 250 mg twice daily. Despite some lightening of the melasma lesions, the hypopigmented lesions persisted and were still accentuated under the Wood's lamp.

Figure 1.

A, Prominent hypomelanotic macules between the background of brown patches on bilateral cheeks after 16th Nd:YAG laser toning. B, The hypopigmented area was accentuated under Wood's lamp. C, The hypopigmented area had 75% repigmentation 6 months after grafting. D, Decreased contrast between the hyper‐ and hypopigmented areas under Wood's light

Therefore, we performed epidermal grafting with an automatic system (Cellutome Epidermal Harvesting System, Acelity, San Antonio, Texas). Informed consent was given by the patient. The study was approved by the Institutional Review Board of MacKay Memorial Hospital (IRB number:17MMHIS052).The hypopigmented area was circled and ablated with an Erbium:YAG laser until pinpointed bleeding was just visible at the base (Figure 2A,B). We chose the inner thigh as the donor site, and 125 micrografts, each 1 mm in size, were harvested in 61 minutes (Figure 2C). We directly transferred the micrografts to the recipient site with a silicone dressing (Figure 2D) and covered the area with steri‐strip and a hydrocolloid dressing. During the first few days, only the outer saturated hydrocolloid dressing was changed if saturated; all other dressings were removed on postoperative day 7. There were some crusts on the erythmatous base of the recipient sites. No scars or hyperpigmentation were noted on the donor sites on the thigh. To prevent exacerbating the melasma lesions, narrowband‐ultraviolet (NB‐UVB) phototherapy after grafting was not recommended. The pigment at the grafted sites started to appear 1 month postoperatively, with a background of erythema. She resumed the tranexamic acid after grafting, and the hyperpigmented area gradually lightened with diminished contrast between the hypo‐ and hyperpigmented areas. The hypopigmented area had 75% repigmentation 6 months after grafting under Wood's light (Figure 1C,D).

Figure 2.

A, The hypopigmented area was circled and marked. B, The hypopigmented area was ablated with an Erbium:YAG laser until pinpointed bleeding was just visible at the base. C, A total of 125 micrografts, each 1 mm in size, were harvested via the epidermal harvesting system. D, The micrografts were directly transferred to the recipient site with a silicone dressing

3. DISCUSSION

The mode of action of 1064‐nm QS Nd:YAG laser toning was subcellular selective photothermolysis (SSP) on stage IV melanosome in the dendrites. In a Zebra fish model, used to investigate selective photothermolysis at the subcellular level by Kim et al., apoptosis was observed when laser irradiation energy was above 0.5 J/cm². Thus, relatively low irradiation energy was required to limit thermal diffusion effects of melanosomes without killing the melanocytes.4However, even if lower sub‐photothermolytic fluences had been used for each laser toning, the total cumulative dose after multiple treatment sessions could have exceeded the total toxic cumulative energy that would destroy the melanocytes eventually.3

The pathophysiology of the leukoderma resulted from repeated QS 1064 nm Nd‐YAG laser toning and photothermal destruction of the melanocytes. This is different from that caused by a CO₂ laser or Erbium laser resurfacing, which demonstrates impairment of melanogenesis but with residual melanocytes and melanin.5 It is postulated that a CO₂ laser or Erbium laser resurfacing was often conducted every 4 to 6 weeks with a total of less than five sessions; therefore, melanocytes were not destructed by repeated phototoxicity. The residual melanocytes facilitated the expediency of repigmentation by topical psoralen photochemotherapy, NB‐UVB phototherapy, ablative fractionated laser, or 308‐nm excimer laser. In contrast, leukoderma or mottled hypopigmentation associated with QS Nd‐YAG laser toning often persists for many years despite a variety of treatments, including topical calcineurin inhibitors and phototherapy, because of lack of melanocytes.1, 3 Weekly targeted NB‐UVB phototherapy and 308‐nm excimer laser treatments have been recommended to provide some clinical improvement,1, 3 but they both can potentially worsen melasma. Therefore, we used epidermal grafting harvested by an automatic system (Cellutome) to transfer normal melanocytes to the hypopigmented area. Its advantages over traditional suction blister epidermal grafting include decreased time, less pain, and no hyperpigmentation at the donor site.6

Melanin absorbs light emitted by Wood's lamp and, thereby, diminishes the intensity of the fluorescence signal. Laser‐induced hypopigmentation can be accentuated under Wood's lamp or UV image under Wood's light from loss of epidermal melanin and decreased melanocytes.1, 3 Therefore, Wood's lamps can help determine whether the lesion is melanocytopenic before conducting a biopsy.

If the lesions are melanocytopenic, either suggested by Wood's lamp examination or shown by biopsy, phototherapy and topical calcineurin inhibitors are expected to have a minimal effect. Epidermal grafting can effectively provide remote melanocytes to the hypopigmented area. Tranexamic acid, an antifibrinolytic agent that targets the vascular component to treat melasma, would be an optimal choice for lightening the melasma lesions, thereby diminishing the contrast between the hyperpigmented and hypopigmented areas. However, topical bleaching agents should be used with caution to prevent worsening of the hypopigmented area.

4. SUMMARY

Repeated Nd‐YAG laser toning can still cause melanocytopenic disorders like leukoderma and mottled hypopigmentation. Wood's light or UV imaging can help observe early leukoderma before it becomes clinically apparent.1 Once leukoderma develops, Wood's light can help determine the degree of melanocytopenia before conducting a biopsy. NB‐UVB phototherapy and a 308‐nm excimer laser can potentially worsen the pre‐existing melasma lesions and may not be effective if the lesions are melanocytopenic. Epidermal grafting is safe and can replenish the hypopigmented area with melanocytes without worsening the melasma.

Wang Y‐J, Chang C‐C. Epidermal grafting for leukoderma resulting from 1064‐nm quality‐switched neodymium‐doped yttrium aluminium garnet laser toning. Int Wound J. 2018;15:1045–1048. 10.1111/iwj.12953