Cigarette smoking as a triggering factor of hidradenitis suppurativa

Background: Hidradenitis suppurativa is a chronic inflammatory skin disease involving the axillary, inguinal and anogenital regions and sometimes, in addition, the submammary or sacral areas. The etiology of this condition is unknown. Objective: A matched-pair case-control study was performed to eva luate the influence of smoking habits on the manifestation of this disease. Methods: Patients who had received surgical treatment for hidradenitis sup purativa in two dermatological centers completed a questionnaire dealing wi th family history, course of the disease and smoking habits. To form a rand omized matched-pair control group, an equal number of patients admitted for various other skin diseases such as atopic dermatitis, varicose veins, ski n tattoos, alopecia areata or melanoma was matched for sex and age and eval uated for smoking habits. Statistical analysis was performed by use of seve ral chi(2) tests in a cross-table setting. Moreover, a comparison to the ex pected smoking prevalence in Germany based on national statistics was perfo rmed. Results: Out of 84 patients treated for hidradenitis suppurativa, 63 subjects (27 men, 36 women) completed the questionnaire. The rate of active cigarette smokers was 88.9% (56 patients), whereas 4 subjects (6.4%) had n ever smoked. 3 patients (4.8%) stated to be ex-smokers, but 2 of these had quit smoking only recently and after onset of the disease. The rate of smok ers in the matched-pair control group was 46%. The significantly higher pro portion of active smokers among patients with hidradenitis suppurativa can be expressed by an odds ratio of 9.4, the calculated 95% confidence interva l was 3.7-23.7 (p < 0.001). The expected smoking prevalence in Germany was 26.7% according to national statistics. 73% of our patients had no family h istory of hidradenitis suppurativa whereas 27% reported at least one affect ed first-degree relative. Conclusion: From the exceedingly high rate of smo kers among patients with this condition we conclude that cigarette smoking is a major triggering factor of hidradenitis suppurativa. Remarkably, the d isease can be categorized as a smoking sequel that is neither of vascular n or neoplastic nature. Because familial occurrence was rather rarely reporte d, and because an environmental factor in the form of cigarette smoking app ears to be of crucial importance to trigger the disease, we assume that the genetic basis of hidradenitis suppurativa is polygenic rather than mendeli an. Smoking cessation should be encouraged particularly in patients with hi dradenitis suppurativa although it is unknown whether this improves the cou rse of the disease.