Pulsed dye laser for nail psoriasis: not the first time and apparently not that efficacious!

Sir,

We read with interest the report by Al-Mutairi and Elkashlan on treatment of nail psoriasis with pulsed dye laser (PDL), published in the May-June edition of the journal.[1] Authors reported a marked reduction in Nail Psoriasis Severity Index (NAPSI) score with improvement in both nail bed and nail matrix lesions after three treatment sessions given by 595 nm PDL monthly. However, this report needs to be critically reviewed for several reasons. In the introductory key learning points, authors clearly state “Pulse dye laser has proved effective for plaque-type psoriasis, but it has not been evaluated in nail psoriasis”.[1] However, at least two studies evaluating the role of PDL in nail psoriasis had already been published by Fernández-Guarino et al. and Oram et al., respectively.[23] Intriguingly, despite their original statement (vide supra), authors conclude with a mention of their results being compatible with those of Fernández-Guarino et al. and Oram et al.[1] Fernández-Guarino et al. were the first to try PDL for nail psoriasis in 14 patients and compared it with photodynamic therapy (PDT) in an intrapatient left-to-right study. They used a 595 nm PDL with 1.5 ms pulse duration, 7 mm beam diameter, and 9.0 J/cm2 energy (parameters that are being followed in all subsequent reports), which was applied in isolation on nails of one hand, while the other side was treated with PDT followed by PDL. Monthly treatments given for 6 months resulted in significant reduction in pain and NAPSI score, which was comparable in both treatment groups. These results were published as early as August 2009.[2] Oram et al. reported similar reduction in NAPSI scores with PDL treatment sessions given monthly for 3 months in 5 patients and published their results in March 2010.[3] Secondly, the treatment response visible in pre- and post-laser photographs seems to be modest. Rather than a significant reduction in pitting, onycholysis, or subungual hyperkeratosis, improvement in paronychia is the most discernible in the photographs. Thirdly, authors gave only three treatment session at monthly intervals and followed the patient for only one month after treatment. In most of the similar studies including the pilot study by Fernández-Guarino et al. and recent studies by Treewittayapoom et al. and Huang et al., six sessions were given because 6 months is the time a nail plate takes to grow completely from matrix to hyponychium.[2345] This is most likely to be the cause for only modest response in their patient, visible in the pre- and post-treatment photographs. Additionally, the mechanism of action of PDL has been mentioned very briefly. Authors could have elaborated on the role of abnormal psoriatic vasculature and dermal angiogenesis in pathogenesis of psoriatic lesions by enhancing epidermal hyperplasia and acting as a conduit for lymphocytes, which are selectively targeted by the PDL. Curiously, authors have not mentioned anything about the tolerability of the procedure or adverse effects, though previous studies have shown pain lasting up to 24 hours as the major side effect,[3] others being transient petechiae and hyperpigmentation.[4]