Isotretinoin and Hidradenitis Suppurativa a Conflictual Binomial: Investigation on Differential Response Rate Between Inflammatory and Follicular Phenotype

ABSTRACT Background Hidradenitis suppurativa (HS) is an inflammatory debilitating chronic skin disease, involving the follicular unit, and its therapeutic management remains challenging. The therapeutic role of isotretinoin in HS and its potential efficacy across different clinical phenotypes remain a matter of ongoing debate. Objectives Our aims were: (1) to determine the potential different response between inflammatory phenotype and follicular phenotype, as defined by Martorell's classification, and (2) to analyze clinical predictors of therapeutic response. Methods We conducted a retrospective observational analysis on consecutive HS patients referring to the Dermatology Department, Fondazione Policlinico A. Gemelli IRCCS—Rome, Italy, between 2019 and 2023, treated with isotretinoin monotherapy at a dosage of 0.5 mg/kg/day for 16 weeks. Results Twenty‐one out of 229 patients affected by HS had been previously treated with isotretinoin, including 13 males and 8 females (mean age 26 ± 5 years; mean BMI 23 ± 2.3). Based on the prevalent clinical manifestations, 12/21 patients showed a follicular phenotype characterized by nodules and multiple comedones, and 9 patients presented an inflammatory phenotype featured by multiple abscesses and draining fistulas. In the follicular phenotype group, the mean IHS4 decreased from 7.6 at baseline to 6.4 after 4 weeks of isotretinoin treatment and to 5.7 at week 8, with no additional improvements at week 16 ( p = 0.01). Mean IHS4 at baseline for the inflammatory group was 14.7, which decreased to 12.3 at week 4 of treatment, and to 11.4 at week 12 with no further improvement at week 16 ( p = 0.218). Overall, 17/21 patients (81%), showed no significant clinical improvement. Only 4 patients (19%) achieved the HiSCR50 after 16 weeks including two non‐smoker females showing follicular phenotype with concomitant acne vulgaris, and two smoker males with normal BMI from the inflammatory phenotype group. Conclusions Although conducted on a small cohort, our findings showed no significant differences in response rates to isotretinoin between the inflammatory and follicular HS phenotypes, as defined according to Martorell's phenotype classification. Further studies on a larger cohort of patients are necessary to confirm our preliminary results.