Defining hidradenitis suppurativa phenotypes based on the elementary lesion pattern: results of a prospective study

Background It has been proposed that two main phenotypes of hidradenitis suppurativa (HS) exist. This proposal is based upon different elementary structures detected in the skin, namely follicular subtypes and inflammatory subtypes. Having an accurate definition of these two variants could help us to better identify patients who may require an early intervention with currently approved targeted immunomodulatory therapies. Objective To define and distinguish between the epidemiological, clinical and analytic characteristics of these two HS phenotypes. Methods An observational, descriptive, non‐randomized and prospective study was conducted. Patients diagnosed with HS between May 2012 and April 2017 by a specialized unit were included. Ultrasound evaluation was performed in all cases. Results About 197 patients were included, 100 women and 97 men, aged between 25 and 47 years. The mean age of onset was significantly different between phenotypes, ranging between 26.69 ± 9.05 in the inflammatory subtype and 17.62 ± 6.42 in the follicular subtype. Follicular subtype patients exhibited a significantly higher number of nodules combined with the presence of multiple commedons (5.65 ± 3.38 versus 0.89 ± 2.72). This contrasted with the higher count of abscesses and fistulas detected in the inflammatory subtype (respectively, 4 ± 2.74 and 3.11 ± 2.56 versus 0.56 ± 1.02 and 0.26 ± 0.56). IgA levels were significantly higher in the inflammatory subtype (497.71 ± 262.26 versus 232.38 ± 84.06). Mean IHS4 score evaluation was higher in the inflammatory subtype (21.04 ± 11.9) compared with the follicular phenotype (7.54 ± 4.66). The inflammatory subtype was found to be an independent risk factor for disease aggressiveness in the multivariate analysis (OR 0.034 [95% CI 0.015–0.072]). Limitations Small sample size. Conclusion Preliminary data suggest the existence of an inflammatory HS phenotype that is associated with higher aggressiveness and major risk of progression during natural history of the disease.