The Hurley system is a popular staging system for Hidradenitis Suppurativa.
Stage 1: Single or multiple isolated abscesses without sinus tract formation or scarring. Stage 1 disease is most common.
Stage 2: Recurrent abscesses with one or more sinus tracts and scarring widely separated by normal skin.
Stage 3: Diffuse or broad involvement with multiple interconnected sinus tracts or abscesses across an entire area with no intervening normal skin.
The Hurley system has diagnostic value but is not suitable for monitoring the efficacy of interventions in clinical trials.
References
http://emedicine.medscape.com/article/1073117-overview
http://www.consultant360.com/exclusives/grading-systems-hidradenitis-suppurativa