Photodynamic Therapy with Intralesional Methylene Blue and a 635 Nm Light-emitting Diode Lamp in Hidradenitis Suppurativa: a Retrospective Follow-up Study in 7 Patients and a Review of the Literature

Hidradenitis suppurativa is a chronic inflammatory skin disease which has an estimated prevalence of 1%. It is characterized by the formation of recurrent painful suppurative nodules and abscesses in the flexural areas of the body. It is believed that its pathogenesis involves an aberrant, genetically-determined activation of innate immunity against the bacterial commensal flora of intertriginous areas. It has been found that the formation of antibiotic-resistant bacterial biofilms is a common finding in hidradenitis lesions. Photodynamic therapy with different compounds and light sources has demonstrated its efficacy in a number of infectious diseases such as nail mycosis and chronic periodontitis. We retrospectively report our experience in the treatment of hidradenitis with photodynamic therapy using intralesional methylene blue and a 635 nm light-emitting diode lamp in 7 patients. Two patients received one session whereas 5 patients received two sessions. At one month follow-up good response was achieved in 6 patients. After 6 months, 5 patients (71%) maintained remission of the disease in the treated area. In view of the results and literature review, we regard methylene blue as an ideal photosensitizer for photodynamic therapy in this disease.