Applications of Lasers in Medical Dermatology

The use of lasers in dermatology has had a major impact on the treatment of many dermatologic conditions. In this column practical applications of lasers in medical dermatology will be discussed to give dermatology residents a broad overview of both established indications and the reasoning behind the usage of lasers in treating these skin conditions. The applications for lasers in aesthetic dermatology are numerous and are constantly being refined and developed; they have been discussed extensively in the literature. Given the vast variety of uses of lasers in dermatology today, a comprehensive review of this topic would likely span several volumes. This article will focus on recent evidence regarding the use of lasers in medical dermatology, specifically laser treatment of selected common dermatoses and cutaneous malignancies.

Laser Treatment of Skin Diseases

Many common dermatoses seen in the dermatologist’s office (eg, discoid lupus erythematosus [DLE], morphea, alopecia) already have an established therapeutic ladder, with most patients responding to either first- or second-line therapies; however, a number of patients present with refractory disease that can be difficult to treat due to either treatment resistance or other contraindications to therapy. With the advent and development of modern lasers, we are now able to target many of these conditions and provide a viable safe treatment option for these patients. Although many physicians may be familiar with the use of the excimer laser in the treatment of psoriasis,¹ a long-standing and well-accepted treatment modality for this condition, many novel applications for different types of lasers have been developed.

First, it is important to consider what a laser is able to accomplish to modulate the skin. With ablative lasers such as the CO₂ laser, it is possible to destroy superficial layers of the skin (ie, the epidermis). It would stand to reason that this approach would be ideal for treating epidermal processes such as viral warts; in fact, this modality has been used for this indication for more than 3 decades, with the earliest references coming from the podiatric and urologic literature.^2,3 Despite conflicting reports of the risk for human papillomavirus aerosolization and subsequent contamination of the treatment area,^4,5 CO₂ laser therapy has been advocated as a nonsurgical approach to difficult-to-treat cases of viral warts.

On the other hand, the pulsed dye laser (PDL) can target blood vessels because the wavelength corresponds to the absorption spectrum of hemoglobin and penetrates to the level of the dermis, while the pulse duration can be set to be shorter than the thermal relaxation time of a small cutaneous blood vessel.⁶ In clinical practice, the PDL has been used for the treatment of vascular lesions including hemangiomas, nevus flammeus, and other vascular proliferations.^7-9 However, the PDL also can be used to target the vessels in cutaneous inflammatory diseases that feature vascular dilation and/or perivascular inflammation as a prominent feature.

Discoid lupus erythematosus is a form of chronic cutaneous lupus erythematosus that may be difficult to treat, with recalcitrant lesions displaying continued inflammation leading to chronic scarring and dyspigmentation. A small study (N=12) presented the efficacy of the PDL in the treatment of DLE lesions, suggesting that it has good efficacy in treating recalcitrant lesions with significant reduction in the cutaneous lupus erythematosus disease area and severity index after 6 weeks of treatment and 6 weeks of follow-up (P<.0001) with decreased erythema and scaling.¹⁰ It is important to note, however, that scarring, dyspigmentation, and atrophy were not affected, which suggests that early intervention may be optimal to prevent development of these sequelae. More interestingly, a more recent study expounded on this idea and attempted to examine pathophysiologic mechanisms behind this observed improvement. Evaluation of biopsy specimens before and after treatment and immunohistochemistry revealed that PDL treatment of cutaneous DLE lesions led to a decrease in vascular endothelial proteins—intercellular adhesion molecule 1 and vascular cell adhesion molecule 1—with a coincident reduction in the dermal lymphocytic infiltrate in treated lesions.¹¹ These results offer a somewhat satisfying view on the correlation between the theory and basic science of laser therapy and the subsequent clinical benefits afforded by laser treatment. A case series provided further evidence that PDL or intense pulsed light can ameliorate the cutaneous lesions of DLE in 16 patients in whom all other treatments had failed.¹²

Several other inflammatory dermatoses can be treated with PDL, though the evidence for most of these conditions is sporadic at best, consisting mostly of case reports and a few case series. Granuloma faciale is one such condition, with evidence of efficacy of the PDL dating back as far as 1999,¹³ though a more recent case series of 4 patients only showed response in 2 patients.¹⁴ Because granuloma faciale features vasculitis as a prominent feature in its pathology, targeting the blood vessels may be helpful, but it is important to remember that there is a complex interplay between multiple factors. For example, treatment with typical fluences used in dermatology can be proinflammatory, leading to tissue damage, necrosis, and posttreatment erythema. However, low-level laser therapy (LLLT) has been shown to downregulate proinflammatory mediators.¹⁵ Additionally, the presence of a large burden of inflammatory cells also may alter the effectiveness of the laser. Several case reports also the show effectiveness of both PDL and the CO₂ laser in treating lesions of cutaneous sarcoidosis, especially lupus pernio.^16-19 Of these 2 modalities, the use of the CO₂ laser for effective remodeling of lupus pernio may be more intuitive; however, it is still important to note that the mechanism of action of several of these laser modalities is unclear with regard to the clinical benefit shown. Morphea and scleroderma also have been treated with laser therapy. It is essential to understand that in many cases, laser therapy may be targeted to treat the precise cutaneous manifestations of disease in each individual patient (eg, CO₂ laser to treat disabling contractures and calcinosis cutis,^20,21 PDL to treat telangiectases related to morphea²²). Again, the most critical consideration is that the treatment modality should align with the cutaneous lesion being targeted.