Prospective comparison study of a 550 picosecond 755 nm laser vs a 50 ns 755 nm laser in the treatment of nevus of Ota

Patchy Dermal Melanocytosis: Differential Diagnosis and Management

BACKGROUND

Nevus of Ito and Mongolian spots are distinct clinical presentations of patchy dermal melanocytosis, characterized by similar dermatological manifestations that can pose diagnostic difficulties for clinicians.

AIM

This review aims to consolidate current understanding and research advancements on these conditions to facilitate clinical diagnosis, differential diagnosis, and management.

METHODS

A comprehensive search of databases including PubMed and Google Scholar was conducted, along with an analysis of pertinent literature retrieved from reference lists spanning nearly four decades.

RESULTS

Epidemiological, clinical, and pathological profiles exhibit nuanced differences between the two conditions, with unique expressions under electron microscopy and the regression possibility. It is noteworthy that most Mongolian spots naturally fade with advancing age, in contrast to nevus of Ito, which persist and may potentially evolve into malignant lesions. While picosecond laser treatment has shown greater efficacy than nanosecond lasers, the lower-energy approach holds particular promise in pediatric cases. The therapeutic landscape for patchy dermal melanocytosis is evolving, shifting from selective photothermal action to photomechanical or subcellular photothermal modalities.

CONCLUSION

This review underscores the importance of meticulous clinical assessment and the potential of innovative therapeutic approaches in managing these conditions.

Ultralow radiant exposure of a short-pulsed laser to disrupt melanosomes with localized thermal damage through a turbid medium

Short-pulsed lasers can treat dermal pigmented lesions through selective photothermolysis. The irradiated light experiences multiple scattering by the skin and is absorbed by abnormal melanosomes as well as by normal blood vessels above the target. Because the fluence is extremely high, the absorbed light can cause thermal damage to the adjacent tissue components, leading to complications. To minimize radiant exposure and reduce the risk of burns, a model of the melanosome-disruption threshold fluence (MDTF) has been developed that accounts for the light-propagation efficiency in the skin. However, the light-propagation efficiency is attenuated because of multiple scattering, which limits the extent to which the radiant exposure required for treatment can be reduced. Here, this study demonstrates the principle of melanosome disruption with localized thermal damage through a turbid medium by ultralow radiant exposure of a short-pulsed laser. The MDTF model was combined with a wavefront-shaping technique to design an irradiation condition that can increase the light-propagation efficiency to the target. Under this irradiation condition, melanosomes were disrupted at a radiant exposure 25 times lower than the minimal value used in conventional laser treatments. Furthermore, almost no thermal damage to the skin was confirmed through a numerical simulation. These experimental and numerical results show the potential for noninvasive melanosome disruption and may lead to the improvement of the safety of short-pulsed laser treatment.

Picosecond alexandrite laser treatment of nevus of Ota in children

BACKGROUND

The picosecond alexandrite laser has been safely and effectively used to treat the nevus of Ota in adults. However, limited data are available for children.

OBJECTIVE

To investigate the efficacy, safety, and correlative influencing factors of a 755nm picosecond alexandrite laser in the treatment of nevus of Ota in children.

METHODS

We retrospectively analyzed Chinese children with nevus of Ota who received a 755nm picosecond alexandrite laser treatment in a tertiary dermatological hospital.

RESULT

A total of 305 pediatric patients received an average of two treatments achieving an average of 79% pigment clearance. After the first treatment, 22 patients achieved complete clearance (95%-100%), and 72 patients achieved excellent response (75%-94%), with an average initial efficacy of 63% lesion clearance. Treatment at an early age achieved better initial efficacy (0- to 12-month group >1- to 6-year group, 6- to 12-year group). And 0- to 12-month group achieved better final efficacy. More treatment sessions also increased the final efficacy. Both initial efficacy and final efficacy were better when treating a darker lesion. The incidence of complications was 12.1%, with 10.8% being post-inflammatory hyperpigmentation and 1.3% being hypopigmentation. The rate of recurrence was 6.6%.

LIMITATION

Retrospective study.

CONCLUSION

A 755nm picosecond alexandrite laser is safe and effective in treating nevus of Ota in children. Younger to initiate treatment, darker lesions, and more treatments are positively associated with better pigmentation clearance.

Advancements in Laser Therapies for Dermal Hyperpigmentation in Skin of Color: A Comprehensive Literature Review and Experience of Sequential Laser Treatments in a Cohort of 122 Indian Patients

The heightened awareness of ethnic dermatology aligns with the growing prevalence of skin of color communities globally, where hyperpigmentation disorders pose a common dermatological challenge. Effectively addressing dermal pigmentation is challenging due to its resistance to conventional therapies and its association with impaired quality of life. This underscores the need for effective treatments and a thorough grasp of laser advancements. A relevant literature search spanning the last 7 years across the PubMed database reveals core studies, challenges, and the evolution of laser technologies tailored for various forms of congenital and acquired dermal hyperpigmentation in skin of color. This comprehensive review explores the mechanisms, applications, and recommendations for pigmentary laser technologies, highlighting the key role of Q-switched lasers in their established millisecond/ nanosecond forms and emerging picosecond lasers, fractional non-ablative and ablative lasers, Intense Pulsed Light, etc. The summary of evidence includes studies on dermal melanocytosis (nevus of Ota and Hori's nevus), tattoos, acquired dermal macular hyperpigmentation, etc., and also entities with mixed epidermal-dermal components, such as melasma and post-inflammatory hyperpigmentation. The review offers valuable insights for clinicians to make informed decisions based on diagnosis, skin type, and the latest technologies to optimize results and minimize complications, especially in darker Fitzpatrick skin types. In their five-year study with 122 Indian patients, the authors applied specific laser combinations for diverse dermal melanoses, including tattoos, dermal/mixed melasma, acquired dermal macular hyperpigmentation, and dermal nevi. Substantial pigmentation reduction, subjectively assessed by both physicians and patients, was observed across all groups. A one-way ANOVA indicated a significant difference in mean improvement scores across various pigmentary conditions (F = 3.39, p = 0.02), with melasma patients exhibiting a significantly higher improvement score than tattoos (p = 0.03). The results affirmed the safety and efficacy of sequential laser therapy for dermal pigmentation in skin of color, advocating for flexibility in approach while maintaining the rationale behind the laser sequences. Despite advancements, challenges persist, and gaps in the current literature are identified. In conclusion, this summary highlights the ongoing pursuit of optimal protocols in dermatological laser treatments for dermal melanoses, offering valuable insights for future research and clinical practice.

Wavelength-dependent threshold fluences for melanosome disruption to evaluate the treatment of pigmented lesions with 532-, 730-, 755-, 785-, and 1064-nm picosecond lasers

BACKGROUND AND OBJECTIVES

A threshold fluence for melanosome disruption has the potential to provide a robust numerical indicator for establishing clinical endpoints for pigmented lesion treatment using a picosecond laser. Although the thresholds for a 755-nm picosecond laser were previously reported, the wavelength dependence has not been investigated. In this study, wavelength-dependent threshold fluences for melanosome disruption were determined. Using a mathematical model based on the thresholds, irradiation parameters for 532-, 730-, 755-, 785-, and 1064-nm picosecond laser treatments were evaluated quantitatively.

STUDY DESIGN/MATERIALS AND METHODS

A suspension of melanosomes extracted from porcine eyes was irradiated using picosecond lasers with varying fluence. The mean particle size of the irradiated melanosomes was measured by dynamic light scattering, and their disruption was observed by scanning electron microscopy to determine the disruption thresholds. A mathematical model was developed, combined with the threshold obtained and Monte Carlo light transport to calculate irradiation parameters required to disrupt melanosomes within the skin tissue.

RESULTS

The threshold fluences were determined to be 0.95, 2.25, 2.75, and 6.50 J/cm² for 532-, 730-, 785-, and 1064-nm picosecond lasers, respectively. The numerical results quantitatively revealed the relationship between irradiation wavelength, incident fluence, and spot size required to disrupt melanosomes distributed at different depths in the skin tissue. The calculated irradiation parameters were consistent with clinical parameters that showed high efficacy with a low incidence of complications.

CONCLUSION

The wavelength-dependent thresholds for melanosome disruption were determined. The results of the evaluation of irradiation parameters from the threshold-based analysis provided numerical indicators for setting the clinical endpoints for 532-, 730-, 755-, 785-, and 1064-nm picosecond lasers.

Update on lasers in pediatric dermatology: how primary care providers can help patients and families navigate appropriate treatment options and timelines

PURPOSE OF REVIEW

The use of lasers in pediatric dermatology is well established, but recent literature has expanded the evidence for specific timelines of treatment. Additionally, new devices and combinations with medical therapy have improved outcomes and treatment options for various conditions.

RECENT FINDINGS

Pulsed dye laser remains the first-line laser for vascular lesions. Recent guidelines support early initiation of laser treatment in port-wine birthmarks to optimize outcomes. For hemangiomas, laser treatment can offer a meaningful addition to oral propranolol therapy. Lasers with shorter wavelengths offer improved outcomes with decreased downtime for pigmented lesions. General anesthesia in the pediatric population continues to be a controversial topic, and the decision to perform laser under general versus topical anesthesia requires discussion with family of risks and benefits.

SUMMARY

Primary care providers can benefit their patients by prompt referral to dermatology for discussion of laser treatment. Port-wine birthmarks require referral in the first weeks of life so that laser treatment can be initiated if appropriate. Although many dermatologic conditions cannot be completely cleared or cured with laser, treatment can offer meaningful outcomes and benefit for patients and families.