Consultant dermatologist Dr Firas Al-Niaimi outlines the various uses of pulsed-dye lasers
Lasers are fast becoming the vogue of dermatology; ranging from ablative, non-ablative, fractional photothermolysis to vascular. Then there are a number of vascular lasers available, including potassium titanyl phosphate (KTP 532 nm), pulsed-dye laser (PDL 95 nm), diode (810 nm) and Nd:YAG (1064 nm). Pulse-dye lasers (PDL) emit light from a rhodamine dye solution and were initially introduced in the 1980s for vascular malformations. Now PDL lasers represent the gold standard vascular laser, with a wealth of evidence to support their use.1
The 595 nm wavelength of PDL lasers targets oxyhaemoglobin found in blood vessels. The main modes of actions are photothermal, including coagulation of the blood and endothelial damage, in conjunction with photochemical effects. Typical vascular lesions which are treated by PDL include port wine stain, haemangioma, telangiectasia, spider angioma and rosacea.1
This article focuses on the use of PDL beyond vascular malformations, which include acne vulgaris, scars, striae, warts, molluscum, psoriasis, rejuvenation, and miscellaneous dermatological indications. I have had significant personal experience in the use of PDL in most of the discussed indications. The effects are either due to targeting the vascular component of a condition, or through photochemical effects; simply explained as biological changes that occur in the skin as a result of the photonic light and tissue interaction. These photochemical changes can result in up or down-regulation of certain pathways or a change in a biological composition and behaviour of the disease.2 The list of conditions which the PDL can treat is growing with more articles being published regularly.
Acne vulgaris is one of the most common skin ailments in adolescents, with a prevalence nearing 90%.3 The mechanism of acne is well-known to be a multifactorial process and its physical and psychological sequelae have a huge impact on quality of life. Although conventional treatment is known to be beneficial in most patients, there are always recalcitrant cases or patients who cannot tolerate traditional antibiotics or isotretinoin due to their side effects.
PDL’s mechanism of treatment in acne is by killing Cutibacterium acnes (one of the known contributory mechanisms) by inducing oxidative stress secondary to the protoporphyrin production by the bacteria, which absorbs the incoming light,4 in addition to photothermal effects on the sebaceous glands and microvasculature which lead to a reduction in the inflammation as well as seborrhoea; two key mechanisms involved in the pathogenesis.5
PDL alone and in combination with topical therapy has been demonstrated to be beneficial.6,7 Seaton et al. found that PDL versus placebo in 41 patients with inflammatory acne demonstrated a significantly better improvement in acne severity in the treatment arm versus the placebo arm at 12-week follow-up.8
Interestingly, there is no conclusive evidence regarding the exact parameters in acne; various parameters have been used with overall good improvement.9
Scars have a multitude of causes, including: burns, acne, trauma and surgery, and are a very common reason for dermatological consultation. The PDL can be used either early on during the proliferative phase of wounding (typically within three months of surgery/trauma), where it has predominantly modulatory effects on the angiogenesis, or at any point of a mature scar where its effects are predominantly a wound-healing pattern that leads ultimately to collagen destruction.10-12 Numerous studies have shown the efficacy of PDL in scars either alone or in combination with other fractional lasers (both ablative and non-ablative).13-15
One study assessed the value of early laser intervention by using PDL to treat surgical scars commencing on the day of suture removal, three weeks following the operation. The research involved a split-scar study and demonstrated a 44% benefit in Vancouver Scar Scale score with PDL as opposed to without it, indicating the benefit of early PDL intervention for scars.16
Striae, also known as stretch marks, are a common presenting complaint and can either be striae rubra or alba. Striae rubra progress to striae alba and both are often refractory to treatment.17 Striae rubra present as linear red plaques that evolve into linear atrophic white plaques. I have previously published a literature review on the treatment options available for striae distensae, systematically appraising the evidence of energy-based treatment for striae available to date.
The results showed that striae alba are more difficult to treat that striae rubra and side effects of all types of laser treatment, such as post-inflammatory hyperpigmentation, were more common in higher Fitzpatrick skin types.17 In a study of 20 patients, PDL has been shown to effectively reduce the erythema in striae rubra, as well as influencing an increase in collagen-1 expression.18
Warts are common and present as papillomatous or hyperkeratotic papules. There is ample evidence to support the use of PDL in warts either alone or in combination with salicylic acid or cryotherapy.19 PDL is efficacious in warts and its mechanism is related partly to coagulation or destruction of the papillary vessels and partly as a thermal effect, leading to clefting of the dermo-epidermal junction in association with a localised inflammatory reaction.20
The number of sessions depends on the thickness and anatomical location of the wart, with the soles of the feet being the slowest to respond, with more sessions required.21 In general, the fluences used are high, in conjunction with a short purpuric pulse duration and no cooling. I have previously published a review paper on the evidence of PDL in warts. In my experience the PDL has a very high success rate if used properly with the correct settings and the required number of treatments. Combination treatment with salicylic acid often yields better results.22
Molluscum contagiosum is a common infectious dermatosis that typically affects children or those who are immunocompromised. I have again previously published a paper systematically reviewing all treatment options available to date. Included in this review are six studies from other authors on the efficacy of PDL in molluscum, demonstrating it is an efficacious and safe laser therapy, with minimal treatments required.23
A study involving 1,250 lesions treated with PDL found that all treated lesions resolved and over a third of patients had no new lesions after just two treatments.24 The exact mechanism of action is unknown and is likely to be immunomodulatory.23,24
Psoriasis is a relatively common inflammatory skin disorder that has been successfully treated with PDL in numerous studies. Different research with assessment in both clinical and laboratory data showed a favourable response with the use of PDL, including when compared to established psoriasis treatments such as vitamin D analogues and phototherapy.
These studies included plaque psoriasis affecting the skin, as well as nail psoriasis which is an entity of psoriasis affecting the nail matrix and plate.25-27 The mechanism is largely immunomodulatory, with changes to the T-cell reactivity, as well as capillary vessels, and an alternation in specific inflammatory markers typically elevated in psoriasis such as E-selectin and substance P.28 There is no uniformity on parameters, with both purpuric and non-purpuric parameters proven effective.29
Lupus is an autoimmune connective tissue disease which can present cutaneously as a butterfly rash on the face or as erythematous plaques and eruptions on photosensitive sites. A variant exists, which is often confined to the skin only and is called discoid lupus. Treatment depends on the subtype, and again can be refractory to conventional treatment of topical steroids or systemics such as hydroxychloroquine.30
Several studies have shown PDL to be effective both as an adjuvant therapy31 and monotherapy32,33 in cutaneous lupus. All the studies indicate that the inflammatory markers decrease post PDL, with clearance of the inflammatory aggregates typically seen histologically in cutaneous lupus.31-33
PDL has also been successfully used in a number of other – less common – dermatological conditions such as angiolymphoid hyperplasia with eosinophilia,34 morphea,35 granuloma faciale,36 and cutaneous sarcoid.37 In most of these cases the series were small and consisted mainly of case reports or series with heterogeneity in terms of parameters used.
Although a primarily vascular laser, the PDL has been used successfully in various non-primary vascular conditions in dermatology. The effects are, in part, due to the treatment of the underlying vascular component, as well as in part due to a photochemical effect; although the exact mechanism in some cases is unknown.
I use the PDL regularly in many of the conditions discussed in this article and advances in this field are ongoing. It should be noted that only suitably-qualified practitioners should use PDL, especially when managing treatments they are not familiar with.
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