Intralesional photodynamic therapy in hidradenitis suppurativa: Getting closer to the target

Background: The successful treatment of hidradenitis suppurativa (HS) with intralesional photodynamic therapy (IL-PDT) has been previously reported in some case series published a few years ago. We present additional data and patient outcome for this form of PDT. Methods: This is an observational retrospective study including all patients diagnosed with HS and treated with IL-PDT in the Hospital Universitari Son Espases from February 2019 to February 2020. Under local or general anesthesia, 5-aminolevulinic acid (5ALA) in gel 2 % or solution 1 % was introduced in the lesion. After two hours, the lesion was intralesionally irradiated (1.4 W, fluence 168 J/cm2) with the tip of a 0.4-mm thick optical fiber connected to a continuous 630-nm diode laser. The main outcome variable was the result (remission, improvement or no change) for each lesion 3 months after the therapy. The result at 6 months and the side effects were secondary outcomes. A multivariate analysis was carried out in order to obtain adjusted odds ratios for no change vs improvement or remission at 3 months for significant variables. Results: A total of 117 lesions (28 nodules and 89 fistulae) were treated in 42 patients. At 3 months, 26 lesions (22.2 %) had resolved, 73 (62.4 %) had improved in size or symptoms, and 18 (15.4 %) experienced no change. The most frequent side effects were skin burns (53 lesions, 45.3 %), and abscess formation (8 lesions, 6.8 %). In the multivariate analysis, significant variables for no benefit were: a higher International Hidradenitis Suppurativa (IHS4) score, active smoking and gluteal and inguinal location. Conclusions: Although our results did not present the level of remission of the previous studies, IL-PDT was useful in most of our patients. Early interventions in patients with lower inflammatory burden were the most valuable.