Dermatology Online Journal

Hidradenitis Suppurativa (HS) is an inflammatory disease that results in abscesses, keloids, and fistulas.   Acne inversa is likely to result from aberrant cellular immunity and dysfunction of the hair follicle in which coagulase negative staphylococcus (CONS) and perhaps other bacteria appear e.g Corynebacterium sp.to play a role by creating biofilms and stimulating the immune system.  One treatment that has been proposed for HS is photodynamic therapy.  The cases series reported are small and not double blinded. As of October of 2104, 8 articles with 64 patients report success with photodynamic therapy using 5-aminolevulinic acid (PDT-ALA) or its methyl ester (PDT-MAL).  One of these 8 reports noted superiority of the free methylene blue gel over niosomal methylene blue gel.  Another report described success in a 27-patient trial using intralesional 5-aminolevulinic acid (ALA) in saline at a concentration of 1%.  This was administered at a dose of 0.2 ml per cm³ and an HS fistula was irradiated by a continuous 630-nm laser diode through a 1-mm thick optical fiber to 1 Watt per cm3 for 3 minutes (180 Joules).  However, 3 articles reported failure with PDT-ALA or pulse dye laser-mediated photodynamic therapy (PDL-PDT) and one article note 1 failure and 1 success.  We suggest that it is the ability of PDT-ALA or PDT-MAL to break up the bio-film produced by CONS and other antibacterial effects that account for its success in treating HS in patients in whom bio-film plays a pivotal part of their pathogenesis.  Other effects are also possible as well.  Other mechanisms by which PDT may improve HS include cytotoxic effects, which cause selective cell necrosis, and immunomodulatory effects.  The data suggests that if PDT is to be used, it should be with MAL or intralesional ALA.

Note that there are a variety of causes of HS. These include hyperkeratosis of in the follicular infundibulum, aberrant cellular immunity, down regulations of defensins in stage III HS, and the infiltration of neutrophils, mast cells, plasma cells, and lymphocytes into the affected follicle, among others.  However, it is likely that in individual cases one cause is primary and others secondary.  In conclusion, PDT is not a first line treatment for HS but in some cases could be added as an adjuvant to therapies such as clindamycin and rifampin.