Photodynamic therapy of necrobiosis lipoidica using methyl aminolevulinate: A retrospective follow-up study

Introduction: Necrobiosis lipoidica (NL) is a rare, treatment-resistant, granulomatous skin disease of unknown origin, frequently seen in patients with diabetes. Methods: In this retrospective study we evaluated the long-term efficacy of methyl aminolaevulinate-based photodynamic therapy (MAL-PDT), including 80 treatments (70 conventional and 10 daylight PDT), on 65 unselected NL patients treated routinely in our clinic. Superficial curettage, avoiding skin oozing or bleeding, was performed prior to MAL application. Results: Conventional MAL-PDT had a 100% cure rate (CR) in 64% (45/70) of the treatment series. With daylight PDT we observed a 100% CR in 80% of the treatment series (8/10), an insignificant difference compared to conventional PDT (p = 0.48). The overall cure rate was 66% (53/80). We observed no correlation between CR and gender, age at first PDT treatment, duration of NL prior to PDT treatment, number of NL elements, or diabetes. New lesions faded, whereas old lesions were clearly visible after inactivation of NL. Discussion: MAL-PDT proved to have full efficacy in 66% of the treatments, with conventional PDT and daylight PDT producing an almost identical result. We observed no correlation between CR and time of follow-up. However, we recommend at least six months to pass before final evaluation of treatment effect.