image of silk fabric and dry skin

J. Y. Lin, MD1 and H. H. Chan, MD, FRCP2

1. Harvard Dermatology Program, Boston, USA
2. Division of Dermatology, Department of Medicine, the University of Hong Kong
and Chinese University of Hong Kong, Hong Kong SAR

ABSTRACT

The development of selective photothermolysis has enabled removal of targets such as melanin. Both lasers and intense pulsed light (IPL) sources have been used in the treatment of pigmented lesions, however careful selection is important to ensure success. This is especially true in darker skinned individuals where the risk of postinflammatory hyperpigmentation (PIH) is high. The advent of the Q-switched laser, IPL, and now fractional photothermolysis (Fraxel®, Reliant Technologies) offers a variety of ways to treat epidermal and dermal pigmentary disorders.

Key Words:
laser, intense pulsed light, Q-switched laser, fractional photothermolysis, pigmentary disorder, postinflammatory hyperpigmentation

In darker skinned individuals photodamage more commonly presents as pigmentary changes rather than wrinkling. This difference is partially due to the higher epidermal melanin content, which can predispose these patients to a higher risk for hyperpigmentation from light source treatment. Although several of these pigmented lesions are common among all skin types, we will focus on the parameters associated with Asian skin.

Epidermal Lesions

Lentigines

Lentigines are common in individuals from sun-exposed sites, and histologically demonstrate melanocyte proliferation without nest formation along the basement membrane. Q-switched (QS) lasers deliver short bursts of wavelength-specific energy that can be absorbed by melanocytes, i.e., QS Nd:YAG lasers (532nm or 1064nm), the QS alexandrite laser (755nm), and the QS ruby laser (694nm). The risk of postinflammatory hyperpigmentation (PIH) in the Asian population is estimated to be about 10%–25% with QS lasers, which have the advantage of achieving significant clearing even after one treatment session and are particularly effective for lightly pigmented lentigines. We routinely test spot, to minimize the risk of PIH. Another approach to removing lentigines is to use longer pulsed lasers in the microsecond domain that match the thermal relaxation time of the epidermis, thus confining the thermal injury to the epidermis.

Without the photomechanical effect associated with the use of QS laser, the risk of PIH associated with long pulsed laser is lower. For example, we use a long pulse 532nm Nd:YAG laser (2ms pulse duration, 6.5J/cm2 fluence, 2mm spot size without cooling or 12 J/cm2 with cooling sapphire window).

Recently, traditional vascular lasers have been employed to remove lentigines. Long pulsed dye laser (LPDL) (595nm) targets both hemoglobin and melanin. Compressing the skin surface during treatment and emptying the blood vessel minimizes damage of the vessels that can lead to bruising and subsequent PIH. A recent study in the treatment of lentigines in Asians, compared the use of LPDL (595nm) (fluence of 10–13J/cm2, pulse duration of 1.5ms) attached with a compression window vs. a QS ruby laser (694nm) (fluence of 6–7J/cm2, pulse duration of 30ns). The LPDL with compression window arm demonstrated superior results and fewer adverse effects.1

Intense pulsed light (IPL) sources that emit a broad band of visible light (400–1,200nm) from a noncoherent filtered flashlamp, affects pigmentation via photothermal effects. IPL has been studied for the treatment of lentigines and ephelides with cutoff filters ranging from 550–590nm, a fluence of 25–35J/cm2, and a pulse width of 4.0ms.2 These studies have been performed on Asian skin with surprisingly no PIH. This lower risk of PIH and the limited postoperative downtime have made IPL a popular choice. The patient should understand, however, that multiple treatments may be necessary. In our practice, for those who do not wish to have any downtime, or for those who wish to improve not only their pigmentation, but also pore size and skin texture, we offer IPL treatment combined with other laser modalities in the same treatment session to obtain a better outcome.

Café au Lait Macules

Café au lait macules are seen at birth and may increase in size over time. Although multiple lesions are associated with neurofibromatosis, café au lait macules are a common finding at birth. They do not signify an increased risk of melanoma and can be removed for cosmetic reasons.

The use of Q-switched lasers in the treatment of café au lait patches has yielded variable results with a high risk of recurrence if pigment is left behind. There have also been reported incidences of paradoxical darkening. Comparison of frequency-doubled QS neodymium:YAG laser (532nm; spot size 2.0mm) and the QS ruby laser (694nm; spot size, 5.0mm) at a fluence of 6.0J/cm2 demonstrated variable responses. Our current approach is to use a long pulsed pigment laser to remove not only the epidermal melanocytes but also the hair follicle melanocytes. Our experience suggests a lower risk of recurrence (~40%) (See Figure 1).

Café au Lait patch prior to treatment, cross-polarized photo.
After 9 treatments with long pulsed alexandrite (755nm, 30–50 J/cm2, 10mm spot size, 3ms pulse width) every 6 weeks, cross-polarized photo.

Figure 1: Left: Café au Lait patch prior to treatment, cross-polarized photo.

Right: After 9 treatments with long pulsed alexandrite (755nm, 30–50 J/cm2, 10mm spot size, 3ms pulse width) every 6 weeks, cross-polarized photo.

Becker’s Nevus

Becker’s nevus, or pigmented hair epidermal nevus, is an uncommon hamartoma that can represent significant cosmetic concern. Histologically, there may be greater pigmentation in the basal region, increased melanophages, and large numbers of irregular, enlarged, smooth muscle fibers in the dermis. In the past, nonspecific treatments such as an argon or CO2 laser were used with associated scarring or permanent hypopigmentation.

We employ long pulse alexandrite 755nm (30–50J/cm2, 10mm spot size, 1.5ms) to target the pigment and surrounding hair follicle. We inform the patients of an approximately 50% success rate after four to eight treatment sessions. Scarring and hypopigmentation are possible side-effects. Other cases report superiority of the erbium:YAG laser 2940nm (28J/cm2, 3mm spot size) as compared to the QS 1064nm Nd:YAG laser (10J/cm2, 10ns pulse width, 3mm spot size).3 In a study of 22 patients treated with one pass mode erbium:YAG laser at 2-year follow-up, 54% achieved complete clearance while >50% improvement was noted by 100% of the patients.3 Slow repigmentation takes place over years but patients should be aware of potential mild permanent hypopigmentation (See Figure 2).

Becker’s nevus on right forearm prior to treatment with diffuse hyperpigmentation and hypertrichosis.
After 8 treatments with long pulsed alexandrite (755nm, 20–30 J/cm2, 10mm spot size, 3ms, pulse width) Note hypopigmentation and mild scarring with loss of hair. Kenacort and 5-FU injections were supplemented to minimize scarring.

Figure 2: Left: A) Becker’s nevus on right forearm prior to treatment with diffuse hyperpigmentation and hypertrichosis.

Right: After 8 treatments with long pulsed alexandrite (755nm, 20–30 J/cm2, 10mm spot size, 3ms, pulse width) Note hypopigmentation and mild scarring with loss of hair. Kenacort and 5-FU injections were supplemented to minimize scarring.

Tips for Laser Treatment of Epidermal Pigmentation:

  • Sun avoidance and/or pretreatment with chemical suppressants of melanin production such as 4% hydroquinone is important before and after the treatment.
  • Test spots should always be done for QS lasers to reduce the risk of PIH.
  • For long pulsed lasers, patients should be warned that several treatments will be necessary to achieve a significant degree of improvement, but there is less downtime and lower risk of PIH.
  • Becker’s nevi can be removed with pigment removing lasers, but there is a risk of recurrence. It is to be further determined whether combination with ablative lasers will have a lower risk of recurrence.

Dermal or Mixed Lesions

Nevus of Ota/Hori’s Nevus

Two forms of primarily dermal pigmentation commonly seen in Asian patients include:

1) Nevus of Ota appears as slate blue pigmentation in a unilateral trigeminal nerve distribution emerging at birth or in young adulthood.

2) Hori’s nevus, also known as acquired bilateral nevus of Ota-like macules (ABNOM), or acquired dermal melanocytosis (ADM), presents as bilateral facial bluish-gray macules. Seen in 0.8% of the Asian population, Hori’s nevus typically affects the malar region, but the lateral temples, alae nasi, eyelids, and forehead can also be involved. Unlike nevus of Ota, the pigmentation in Hori’s nevus is acquired and does not involve the mucosa. Not uncommonly, melasma and Hori’s nevus can present concurrently.

The treatments for both types of dermal pigmentation are similar and again include the QS lasers. QS ruby (694nm), QS Alexandrite (755nm), and QS 1064nm Nd:YAG have all been used for the treatment of nevus of Ota with excellent results and similar minimal risk of complications. In our retrospective study of 46 children and 107 adults, >75% achieved a complete response with Q-switched ruby (694nm wavelength, 30ns pulse duration, 4mm spot size, 5–7J/cm2 fluence at 3–4-month intervals). Treatment is optimal at a younger age, as there is a lower number of mean treatments and lower rate of complications.4

Compared to nevus of Ota, Hori’s nevus is particularly challenging to treat and there are at least two potential reasons for this: 1) melanocytes are located perivascularly leading to a higher likelihood of PIH after laser therapy, and 2) there is a frequent association with melasma and thus, the associated presence of epidermal pigmentation. As such, combination approaches are frequently used.

Recently, the concurrent use of QS 532nm Nd:YAG in combination with the QS 1064nm Nd:YAG laser in a small study was shown to be more effective in reducing the degree of pigmentation of Hori’s nevus.5 Other employed techniques include the use of topical bleaching agents such as 0.1% tretinoin aqueous gel and 5% hydroquinone ointment containing 7% lactic acid to discharge epidermal melanin 4–6 weeks prior to treatment. PIH was documented in 10.5% of these cases as opposed to 50%–73% of patients in prior studies.6 We also treat our patients with both preoperative and postoperative topical bleaching agents.

The main issue for patients with Hori’s nevus is the downtime associated with frequent use of QS lasers. We are currently investigating the use of contact cooling together with a pulsed light source at the red light region (690–1000nm). The aim of this treatment is to achieve removal of these lesions by inducing apoptosis of the melanocytes after repeat treatments, and to reduce downtime.

Melasma

Melasma is a common yet difficult to treat pigmentary disorder, typically found symmetrically on the face of women. Risk factors include sun exposure, increased hormones, genetic predisposition, and phototoxic medications. While topical agents remain the first-line treatment for epidermal and mixed type of melasma, a laser or light source has been used for the more refractory lesions.

IPL theoretically offers an attractive alternative with minimal downtime, but may not be an effective, long-term treatment as a solo agent. IPL, used at 570nm and 590–615nm filters in 4-week intervals for a total of four treatments, was tested on Asian patients. There was a 39.8% improvement of the relative melanin index in the treatment groups compared with 11.6% improvement in the control group at week 16. There was however, repigmentation at the end of the 36-week treatment suggesting that maintenance therapy may be necessary.7 Patient expectations should include microcrust formation 2–3 days after irradiation with resolution within 1–2 weeks. QS 1064nm Nd:YAG laser (6mm spot size, 1.6J/cm2) can also be used for the treatment of melasma. Mild erythema can be used as the clinical endpoint and patients will require monthly treatment. The newest addition to the armamentarium is fractional photothermolysis (FP) (Fraxel®, Reliant Technologies). FP involves the use of an infrared laser (1450nm or 1540nm) to create microcolumns of thermal injury surrounded by uninjured tissue. The columns of thermal injury surrounded by uninjured tissue are called microscopic treatment zones (MTZs). The density of MTZs can be varied for a given energy level. Reported side-effects are sunburn-like erythema that lasts 1–3 days. The original proof of principle study by Tannous, et al. demonstrated a marked reduction in both epidermal and dermal pigmentation 6 months after two full face FP treatments spaced 3 weeks apart.8 In a 10 patient study (Fitzpatrick skin types III-V) with 6–12mJ/MTZ and 2,000–3,500MTZ/cm2 for 4–6 treatments, 60% of the patients had 75%–100% clearing. Only 1/10 patients had PIH.9

We recently published an abstract on a study of 16 Asian patients using a lower dose of 125MTZ/cm2 at energy of 8mJ, every 2–4 weeks. Lower energy and density reduced pain and downtime. High density is not significantly effective and has a risk of hyperpigmentation in this skin-type population. The selective MTZs created by FP have been studied histologically. Microscopic epidermal necrotic debris (MENDs) forms by day 1 and is shed with the epidermis within 7 days. MENDs has been shown to contain melanin pigment and may serve as a “melanin shuttle”, which is rapidly eliminated by the keratinocyte migration from the borders of the MTZs. Furthermore, there is decreased melanin content in the basal cell layer after treatment. There was no reported relapse in melanin pigment at 3 months.10

Tips for Laser Treatment of Dermal and Mixed Pigmentation:

  • A Wood’s lamp is helpful in determining the degree of epidermal and dermal components. Cross-polarizing magnification can help distinguish the 2 components during treatment.
  • Reducing epidermal pigmentation with topicals or normal pulse laser may allow for deeper penetration of pigment lasers.
  • Before and after photography is essential to help the patient appreciate improvement.

Conclusions

  • Epidermal pigmentation is effectively targeted with Q-switched lasers. Pretreatment with melanin-inhibitory substances, longer pulse duration, and compression of vessels can help reduce the risk of PIH.
  • IPL is an effective method of removing epidermal pigmentation with reduced downtime, but may require multiple treatments.
  • Dermal pigmentation may be best treated with a combination of lasers such as Q-switched 532nm Nd:YAG in combination with the 1064nm laser.
  • FP is an effective treatment of melasma and reduced density is important in the Asian skin type to reduce the risk of PIH.

References

  1. Kono T, Manstein D, Chan HH, et al. QS Ruby versus long-pulsed dye laser delivered with compression for treatment of facial lentigines in Asians. Lasers Surg Med 38(2):94-7 (2005 Nov).
  2. Kawada A, Shiraishi H, Asai M, et al. Clinical improvement of solar lentigines and ephelides with an intense pulsed light source. Dermatol Surg 28(6):504-8 (2002 Jun).
  3. Trelles MA, Allones I, Moreno-Arias GA, et al. Becker’s naevus: a comparative study between erbium: YAG and Q-switched neodymium:YAG; clinical and histopathological findings. Br J Dermatol 152(2):308-13 (2005 Feb).
  4. Kono T, Chan HH, Ercocen AR, et al. Use of Q-switched ruby laser in the treatment of nevus of Ota in different age groups. Lasers Surg Med 32(5): 391-5 (2003 May).
  5. Ee HL, Goh CL, Khoo LS, et al. Treatment of acquired bilateral nevus of ota-like macules (Hori’s nevus) with a combination of the 532nm Q-Switched Nd:YAG laser followed by the 1,064nm Q-switched Nd:YAG is more effective: prospective study. Dermatol Surg 32(1):34-40 (2006 Jan).
  6. Momosawa A, Yoshimura K, Uchida G, et al. Combined therapy using Q-switched ruby laser and bleaching treatment with tretinoin and hydroquinone for acquired dermal melanocytosis. Dermatol Surg 29 (10): 1001-7 (2003 Oct).
  7. Wang CC, Hui CY, Sue YM, et al. Intense pulsed light for the treatment of refractory melasma in Asian patients. Dermatol Surg 30 (9): 1196-200 (2004 Oct).
  8. Tannous ZS and Astner S. Utilizing fractional resurfacing in the treatment of therapy-resistant melasma. J Cosmet Laser Ther 7(1): 39-43 (2005 Mar).
  9. Rokhsar CK and Fitzpatrick RE. The treatment of melasma with fractional photothermolysis: a pilot study. Dermatol Surg 31 (12): 1645-50 (2005 Dec).
  10. Laubach HJ, Tannous Z, Anderson RR, et al. Skin responses to fractional photothermolysis. Lasers Surg Med 38(2):142-9 (2006 Jan).
STL Volume 11 Number 8

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