深在性太田母斑に対するQスイッチヤグレーザー照射とQスイッチルビーレーザー照射の比較検討

Abstract

Lasers have attracted close attention among the currently available methods for their potential capacity to produce little discomfort, minimize scarring, and require few skills. There have not, however, been any laser systems with the efficacy to treat“true”deep seated dermal melanin pigmentation lesions as deep, deep dominant, and diffuse types of Ota's nevus. Recent reports have suggested use of the Q-switched ruby laser (Q-Ruby) and the Q-switched Nd: YAG laser (Q-YAG) achieved success in treating nevi. The effectiveness of these two laser systems against“deep seated”Ota's nevus has yet to be definitely determined in clinico-pathological observations.The authors evaluate the efficacy of the Q-YAG and the Q-Ruby against the“deep seated”Ota's nevus, comparing the effectiveness of the two laser systems both clinically and histopathologically.A total of 42 deep-seated Ota's nevus lesions of 20 patients were treated. Prior to treatment, all lesions were confirmed as the deep seated group of Ota's nevus, that is, one of the deep (De), deep dominant (DD), or diffuse (Di) types by skin biopsy. Q-YAG laser (NIIC: IS201, and Con-Bio: Medlite) having a wavelength of 1064nm and a pulse width of 10 nsec, and Q-Ruby laser (Spectrum: RD-1200) having a wavelength of 694nm and a pulse width of 25 nsec were used in the trials. Laser irradiation was conducted under local or general anesthesia. Each irradiation of Q-YAG and Q-Ruby was separately performed only one time at the same lesion of the same patient. The fluences used were between 7.0 and 8.0 J/cm2. After laser irradiation, biopsies were chronologically performed for both photo- and electron-microscope observation of post-irradiation change. The clinical effectiveness of Q-YAG and Q-Ruby at each treated site was judged over a period of three months after irradiation.The total effective rates of Q-YAG and Q-Ruby on deep-seated Ota's nevus were 41% and 33% respectively. Although there was no significant difference between Q-YAG and Q-Ruby in their respective effective rate according to lesional sites, there was prominent difference between the two lasers in histological effectiveness; on Type DD, the effective rates of Q-YAG and Q-Ruby were 38% and 13% respectively, and on Type De, they were 20% and 10% respectively. This difference was more prominent in such thick skin lesions as cheek and temple than in eyelid. The aforementioned more favorable results produced by Q-YAG than by Q-Ruby are thought attributable, not to 694nm wavelength ·dependent melanin-selective advantage of Q-Ruby, but to 1064nm wavelength-dependent penetration advantage of Q-YAG; the healing clearance of pigmentation at the deep dermal layer in deep-seated Ota's nevus depends more strongly on the ability of lesional penetration than on that of lesional selectivity.