Mimi Tran, MD1 and Vincent Richer, MD, FRCPC, FAAD1,2

1Department of Dermatology and Skin Science, University of British Columbia, Vancouver, BC, Canada
2Pacific Derm, Vancouver, BC, Canada

Conflict of interest:
All of the authors have no conflicts to declare for this work.

Abstract:
Dermatosis papulosa nigra is a benign skin lesion found most frequently on the face of patients with skin of color. Elective treatment is occasionally requested. However, in view of knowledge gaps regarding aesthetic treatments for skin of color, patients can be exposed to unnecessary risks or simply denied treatment options due to physician reservation. Cosmetic treatments should balance efficacy of lesion removal while minimizing pigmentary complications. In this review, we describe the few published treatment modalities for dermatosis papulosa nigra. Alongside established surgical techniques, laser devices including the 532-nm potassium-titanyl-phosphate laser, 532-nm diode laser, 585-nm pulsed dye laser, 1064-nm neodymium-doped yttrium aluminum garnet laser, 1550-nm erbium-doped fractionated laser and the 10,600-nm carbon dioxide laser have been successfully reported. The insight from this review can assist in increasing our understanding of safe and effective treatments for conditions that are common on skin of color.

Key Words:
dermatosis papulosa nigra, laser, skin of color

Introduction

Dermatosis papulosa nigra (DPN) is a benign skin lesion found in patients with skin of color, particularly in individuals of African or Asian descent.1-4 Lesions are often categorized as a variant of seborrheic keratosis and preferentially occur on the face.4 They are associated with similar FGFR3 gene mutations as seborrheic keratosis.4-6 However, unlike seborrheic keratosis, DPN tend to present earlier in life and are more commonly found in women.1,5,7,8 Histopathological findings show similarities to acanthotic seborrheic keratosis.1-3 On dermoscopy, DPN show comedo-like openings, fissures and ridges representing a cerebriform-like pattern.1,7 Clinically, they present as brown papules that are typically asymptomatic but can have associated pruritus.3,9 Although they are benign in nature, DPN can be cosmetically displeasing and patients occasionally seek elective removal. Physician reservations and knowledge gaps concerning aesthetic treatments for skin of color are widespread, especially when it comes to the use of energy-based devices.10 Consequently, patients may be denied the opportunity to discuss available options or exposed to additional unnecessary risks, especially adverse pigmentary changes with inappropriate treatment selection. This knowledge gap applies to the treatment of DPN and creates an opportunity for review of published elective therapeutic procedures.

Treatment options for DPN include surgical techniques, such as cryotherapy, curettage, and electrodessication, as well as laser therapy. Many laser options for DPN have been documented, including the 532-nm potassium-titanyl-phosphate (KTP) laser, 532-nm diode laser, 585-nm pulsed dye laser (PDL), 1064-nm neodymium-doped yttrium aluminum garnet (Nd:YAG) laser, 1550-nm erbium-doped fractionated laser, and the 10,600-nm carbon dioxide (CO2) laser. Adverse effects of treatment include pain, crusting, dyspigmentation, scarring, and recurrence. The ideal treatment would be effective at clearing the lesions while circumventing pigmentary complications that conventional surgical treatments can produce, especially in a disorder common on skin of color.

Treatment Modalities of DPN: Advantages, Disadvantages and Adverse Events

Scissor Excision

The treatment of DPN using simple scissor excision is overall well tolerated, with bleeding, erythema, and edema being the most common acute adverse events.11 Pedunculated lesions of DPN are the most amenable to scissor excision.12 Common tools include fine curved scissors, used with or without local anesthesia, and post-procedure wound care consists of petrolatum or topical antibiotic application. Although there are few studies reporting outcomes for scissor excision, we suspect adverse events to be similar with other surgical excisions of epidermal lesions including pain, hemorrhage, dyspigmentation, scar, and recurrence.

Cryotherapy

Cryotherapy has the advantage of being inexpensive and fast, with minimal pre-procedure preparation.13 However, limited peer-reviewed studies on the success of DPN treatment with cryosurgery have been published. Depending on the depth of the lesion and provider technique, number of treatments and freeze-thaw cycles may vary.14,15 The chief concern with this modality in patients with skin of color is hypopigmentation, caused by damage to melanocytes in underlying or surrounding healthy skin. As such, this modality should be used with extreme caution.16

Curettage

Curettage is another surgical option for epidermal tumors. As with cryotherapy, the cost is minimal. Different size curettes can be used depending on size of DPN. Anesthesia is typically administered prior to the procedure, however, studies have reported treatment without anesthesia with minimal adverse outcomes.15 Kauh et al. described 20 cases treated with light abrasive curettage without local anesthesia as an effective treatment for DPN with no scarring.15 In one study, curettage had higher mean clearance rates for the treatment of DPN compared to electrodessication and pulsed-dye laser, although the rates were not statistically significant.17 The main concern with curettage is risk of pigment changes and cosmetically unacceptable scars.

Electrodessication

Electrodessication is routinely used in the treatment of epidermal tumors including seborrheic keratoses, warts, acrochordons, and DPN. Wall-mounted electrosurgical units are most commonly used for DPN.17,18 The voltage is set lower and titrated up, with studies showing an average setting of 0.6-1.0 W. Pain is a common complaint during procedures and thus local or topical anesthesia can be used prior to treatment. Kundu et al. showed that DPN improvement was comparable between electrodessication and KTP laser.19 However, patients preferred KTP laser due to comfort.19 Notably, in this study, no anesthesia was provided to the electrodessication group. Garcia et al. demonstrated that electrodessication was the most preferred modality for cosmetic outcomes compared to PDL and curettage for treating DPN, and showed comparable treatment outcomes, although findings were not statistically different.17

532-nm Potassium-titanyl-phosphate Laser and 532-nm Diode Lasers

At 532-nm, the long-pulse KTP laser is most commonly used to treat vascular skin lesions. The KTP laser is a Nd:YAG laser whose beam is directed through a non-linear frequency-doubling potassium-titanyl-phosphate (or most recently, lithium borate) crystal, producing a beam in the green visible light spectrum.20 Like the PDL, the KTP can also be absorbed by melanin and thus can be used in pigmented lesions, including solar lentigines.21 There are two splitface splitface studies highlighting KTP laser as a treatment for DPN. Compared to electrodessication, Kundu et al.19 showed that 75% of patients (n=14) displayed 76-100% improvement using 1 mm spot, 10 ms pulse at 15 J/cm2. The efficacy was comparable to electrodessication. Joshi et al.22 performed a similar study with 15 patients showing comparable efficacy between KTP laser and electrodessication, but approaching significance in favor of KTP laser. In both studies, patients rated KTP laser as less painful and more favorable compared to electrodessication. Similar findings showed excellent treatment response with mild postinflammatory hypopigmentation using the 532-nm diode laser with settings of 700 to 1000 microns spot size, 8-16 J/cm2 settings to treat DPN.23,24

Pulsed Dye Laser

With a wavelength of 585-nm, PDL has a high affinity for oxyhemoglobin and thus is used for many vascular skin conditions. Large structures containing melanin can also absorb PDL energy, particularly if used with a longer pulse duration.25 Using a 7 mm spot size, 10 J/cm2 and 10 ms pulse duration, one treatment using PDL showed similar treatment outcomes compared to curettage and electrodessication.17 Although not significantly different, findings did show that PDL was more painful. Favorable improvement and outcomes were achieved with 7 mm spot size, 8-9.5 J/cm2 with 10 ms pulse duration PDL in one case report, but required 2-6 sessions to achieve these results.26

Q-switched and Picosecond Lasers

Though not formally reported in the scientific literature, Q-switched and picosecond range lasers with wavelengths targeting pigment such as 532-nm, 694-nm, 755-nm and 1064-nm are used in clinical practice to treat DPN. It is believed that due to the short pulse duration resulting in less photothermal and more photomechanical effects, picosecond lasers may reduce the risk of postinflammatory hyperpigmentation.

Neodymium-doped Yttrium Aluminium Garnet laser

Two patients with DPN achieved excellent results in one treatment with the long-pulsed Nd-YAG at 3 mm spot size, 145-155 J/cm2, and 20 ms pulse duration.12 The patients required no anesthesia and reported minimal discomfort.

Resurfacing Lasers: Erbium-doped 1550-nm Fractionated Laser

Non-ablative resurfacing has become the treatment of choice for a broad range of aesthetic indications. Non-ablative water-targeting lasers allow for shorter downtime and less complications. One case report showed a successful treatment of DPN using a 1550-nm wavelength erbium-doped laser at 60-70 mJ, treatment level 7, 20% coverage, 2.42-2.94 kJ total energy, with 8-10 passes over 3 treatments.27 Topical anesthetic was used prior to treatment.

Resurfacing Lasers: Carbon dioxide (CO2) Laser

Ablative lasers are another well-established option to treat epidermal tumors. Carbon dioxide laser is one of the oldest gas medium ablative laser devices and there is significant clinical experience in treating a variety of conditions including nevi, verruca, keloids, and acne scarring. A retrospective study showed high satisfaction of patients who received CO2 laser treatment on DPN with no post-procedural complications, although there was a 28% recurrence rate.28 Bruscino et al.29 used spot size of 0.7 mm, 0.5-0.7 W, and 10 Hz to treat 5 female patients with DPN, resulting in excellent response and no recurrence.

Discussion

Given its benign nature, any elective treatment for DPN should balance results with potential adverse events including pain, dyspigmentation, scarring and recurrence. Patients must be clearly counselled that treatment is not medically necessary and that it will not change the natural history of this condition over time. They should be directed to providers with experience in treating skin of color.

When treating DPN, surgical modalities can require longer preparatory time for anesthesia. Bleeding can also be a problem for surgical excision or curettage, especially if multiple lesions are excised or if a patient is anticoagulated. Although a quick procedure, cryotherapy can cause significant pigmentary change, especially in skin of color. Electrodessication can result in satisfactory results, but pain is common and time should be allotted for anesthesia. Given their low costs and convenience, surgical modalities are widely available.

Laser treatment options for DPN are vast and summarized in Table 1. A major advantage to KTP or PDL lasers is the absence of pre-procedure anesthesia. The number of treatments depends on DPN size, wavelength chosen, laser settings, and operator technique. Given that the treatment zone is small, methods that help prevent damage to adjacent normal skin should be prioritized. The precise control of treatment is more difficult in surgical techniques, particularly in cryotherapy and curettage. Empirically in our practice, we preferentially use a long-pulse KTP laser with a small spot size and parallel contact cooling to precisely target DPN. Pulse-stacking is often necessary to reach a superficial whitening reaction on the lesion or until a faint “pop” is heard. Scaling and crusting of the lesions last for 5-10 days. Aftercare involves strict sun avoidance and liberal use of emollients until the treated areas have shed. The effectiveness, recovery and side effect profile of this modality has been very favorable in our hands (Figure 1). Anecdotally, patients who have experienced both KTP laser and electrodessication in the past have reported higher levels of satisfaction and more manageable “down time” with KTP laser.

Hyperpigmentation is one of the most dreaded potential side effects when using surgical techniques to treat DPN. Postinflammatory hypo or hyperpigmentation can be mitigated with several techniques focusing on decreasing inflammation or melanin production post-procedure. There is, however, a lack of global evidence-based consensus regarding the most effective approach. Topical hydroquinone, usually in 2-4% concentration, can be used alone or in combination with tretinoin, azelaic acid or kojic acid as tolerated.30 Topical corticosteroids, both mid to high potency, have also been reported immediately after the procedure and for short durations to prevent post-inflammatory hyperpigmentation.31 Most importantly, strict pre and post-treatment sun avoidance should be recommended with broadspectrum ultraviolet (UV) A and UVB protection to prevent melanocyte stimulation. In the majority of studies identified in our review, post-inflammatory pigment changes in the treatment of DPN resolved within a year.

 

 

YearReferencesTreatment# of Treatments# of PatientsTreatment SettingsPost-treatmentResults
Case Reports and Case Series
2001Spoor T23Diode 532-nm1-234700 to 1000 microns spot size, 8-16 J/cm2. Some patients required 4% topical lidocaine.NoneTreated lesions hyperpigmented then sloughed off over 3 weeks. Mild hypopigmentation in one patient which resolved. Overall, patient acceptance and response were excellent.
2007Lupo MP24Diode 532-nmNot reported1700 nm handpiece set at 12 J/cm2, 2 W, 6 Hz, 15 ms pulse duration. No topical anesthetic.Gentle cleanserNo pigmentary changes were noted.
2015Karadag AS, et al.26PDL 585-nm2-617 mm spot size, 8-9.5 J/cm2, 10 ms pulse duration.Not reportedMild pain, post-procedural erythema and edema were observed but resolved. Good improvement after 2-6 sessions with no post-procedural complications or recurrence.
2008Schweiger ES, et al.12Nd:YAG 1,064-nm12Long-pulsed. No anesthesia. 3 mm spot size, 145-155 J/cm2, 20 ms pulse duration.Petroleum jellyExcellent results. 90% treated lesions had no pigmentary changes. Of the lesions with pigmentary changes, no post-treatment pigmentation was noted at 7 months.
2013Bruscino N, et al.29CO2 10,600-nm1-250.7 mm spot size, 0.5-0.7 W, 10 Hz. No surface anesthesia.Topical antibiotic and sunscreenMild pain. Results were excellent and immediate with no recurrence at 8 months.
2016Ali FR, et al.28CO2 10,600-nmNot reported18Topical anaesthesia using EMLA cream. Test patch of laser ablation is undertaken using super-pulse mode (smaller papules; 1 W, 100 ms pulse) or resurfacing mode (larger plaques; 10 W, 2 mm spot size)Soft paraffin ointment is applied dailyMedian response was 9.5 (range 6-10) with 9 patients citing the maximum score of 10 for satisfaction. No post-procedure complications were noted.
Publications Comparing Treatment Modalities
2008Joshi S, et al.22KTP 532-nm vs. electrodessication (split-face)215Not reportedNot reportedKTP laser and electrodessication were statistically equivalent for efficacy. Patients were less uncomfortable with KTP.
2009Kundu RV, et al.19KTP 532-nm vs. electrodessication (split-face)21415 J/cm2, 10 ms pulse duration. No anesthesia.Not reportedNo significant treatment difference between KTP and electrodessication. KTP laser was preferred over electrodessication for comfort.
2010Garcia MS, et al.17PDL 585-nm vs. curettage vs. electrodessication (4 lesions selected: 1 for each therapy and a control)1107 mm spot size, 10 J/cm2, 10 ms pulse duration.4% hydroquinone cream applied BID, petroleum jelly BID, and photoprotectionMean lesion clearance was 88% for laser
compared to 96% for curettage and 92.5% for electrodessication, but statically no difference. Patients rated the laser as most painful. Hyperpigmentation was noted in all 3 modalities.
Table 1: Summary of published evidence on laser treatment for dermatosis papulosa nigra.

PDL = pulse dye laser; KTP = potassium-titanyl-phosphate; Nd:YAG = neodymium-doped yttrium aluminium garnet; CO2 = carbon dioxide

Patient of South Asian descent pictured before and 8 weeks after one treatment session with a long-pulse 532-nm laser
Figure 1: Patient of South Asian descent pictured before and 8 weeks after one treatment session with a long-pulse 532-nm laser. The Excel V® laser by Cutera® was used at 11 J/cm2 fluence, 3 mm spot size, 6 ms pulse duration, 10 degrees Celcius contact cooling and 1.0 Hz repetition. Pulse-stacking (3-4 pulses) was necessary to obtain the endpoint (faint popping sound or superficial whitening/scaling).

Conclusion

This literature review demonstrates that, in many ways, the large number of treatment options for DPN reported is a direct reflection of the absence of consensus regarding the best option. The few studies comparing treatment modalities head-to-head point to comparable efficacy, but more favorable satisfaction/ tolerance using KTP laser when compared to electrodessication. As the body of evidence grows, we look forward to seeing expanding options and increased safety in the treatment of conditions that are common on skin of color, such as DPN.

References



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