Phage Therapy for Hidradenitis Suppurativa: a unique challenge and opportunity for personalized treatment of a complex, inflammatory disease.

Phage therapy is an emerging antimicrobial treatment for critical multidrug resistant pathogens. In this review, the specific potential and challenges of phage therapy for patients suffering from hidradenitis suppurativa (HS) are discussed. This represents a unique challenge as HS is a chronic inflammatory disease, but presenting with acute exacerbations, which have an enormous negative impact on the patient's quality of life. The therapeutic arsenal for HS has expanded the last decade e.g. with adalimumab and several other biologicals that are currently under investigation. However, treatment of HS remains challenging for dermatologists because of both primary and secondary non-responders to all classes of the current treatment options. Furthermore, after several courses, a patient may lose response to therapy, meaning long-term use is not always an option. Culturing studies and 16S ribosomal RNA profiling highlight the complex polymicrobial nature of HS lesions. Despite the detection of various bacterial species in lesion samples, several key pathogens, including Staphylococcus, Corynebacterium and Streptococcus, can be pointed out as potential targets for phage therapy. Using phage therapy for the treatment of a chronic inflammatory disease could provide new insights into the role of bacteria and the immune system in HS development. In addition, potentially more details on the immunomodulatory effects of phages may come to light.