Defining Moderate Disease and Progression in Hidradenitis Suppurativa: An Expert Framework to Unlock the Window of Opportunity for Prompt Treatment

The concept of a therapeutic window of opportunity, defined as the period from symptom onset during which treatment initiation yields the most favorable patient outcomes, is applied in routine clinical practice across a range of inflammatory conditions. It has become an increasingly important area of interest in hidradenitis suppurativa (HS), a disease in which recurrent inflammation and accumulating damage can lead to irreversible destruction of skin architecture. Biologic therapies, aiming to suppress the inflammatory burden and prevent disease progression, are currently only permitted in moderate to severe HS. However, as there is no consensus definition of moderate disease, physicians may face uncertainty about when to consider or switch biologic therapy. To identify the boundaries of the window of opportunity within HS, global HS experts have developed frameworks for defining moderate HS and disease progression. It is proposed that prompt medical treatment should be administered to patients with moderate HS, defined as patients with inadequate control of HS symptoms on conventional therapies, or one inflamed skin tunnel (draining/non-draining), or four or more inflammatory lesions (including inflammatory nodules and abscesses) involving two or more anatomic areas. Furthermore, the proposed definition for disease progression is the development of one or more new tunnel(s) and/or the extension of existing tunnels, or development of one or more persistent HS lesions in an anatomical region not previously affected, or any increase in the number of persistent HS lesions in an affected anatomical region. The proposed frameworks aim to provide practical advice to physicians and support targeting the window of opportunity during routine clinical practice.