Hidradenitis suppurativa: Evaluating activity patterns and predictors of recalcitrant course-A population-based study.

Background: Epidemiological evidence regarding the course and activity patterns of hidradenitis suppurativa (HS) is yet to be delineated.

Objective: To identify activity patterns of HS throughout the time axis and to outline predictors of recalcitrant disease course.

Methods: A population-based retrospective cohort study was performed to follow patients with HS (n = 4417) throughout the initial 10 years following their diagnosis. The disease was considered active in a certain month if one of the following criteria was fulfilled: (i) purchase of an HS-related drug, (ii) admission to a dermatological ward and (iii) referral to a dermatological consultation in an emergency room. Patients with a recalcitrant disease were defined as those with ≥5 years of follow-up with ≥6 'active months' each. Patients with an indolent course were defined as those experiencing ≥9 years of follow-up with ≤1 'active months' each.

Results: The average (SD) number of months in which patients had an active disease was 1.37 (1.28) months per year. While 98 (2.2%) patients pursued a recalcitrant course, 1390 (31.5%) went through an indolent disease course. Older age (≥38 years; adjusted OR, 6.17; 95% CI, 3.33-11.43), Arab ethnicity (adjusted OR, 2.04; 95% CI, 1.20-3.48), low socioeconomic status (adjusted OR, 1.64; 95% CI, 1.03-2.60), obesity (adjusted OR, 3.47; 95% CI, 2.25-5.34) and smoking (adjusted OR, 2.65; 95% CI, 1.57-4.47) were found to independently predict recalcitrant course of HS.

Conclusions: Mild course is more frequently encountered than severe course among Israeli patients with HS. Modifiable risk factors of recalcitrant course should be carefully addressed.