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 evaluate the influence of smoking habits on the manifestation of this disease.
METHODS: Patients who had received surgical treatment for hidradenitis suppurativa in two dermatological centers completed a questionnaire dealing with family history, course of the disease and smoking habits. To form a randomized matched-pair control group, an equal number of patients admitted for various other skin diseases such as atopic dermatitis, varicose veins, skin tattoos, alopecia areata or melanoma was matched for sex and age and evaluated for smoking habits. Statistical analysis was performed by use of several chi2 tests in a cross-table setting. Moreover, a comparison to the expected smoking prevalence in Germany based on national statistics was performed.
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 never 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 smokers in the matched-pair control group was 46%. The significantly higher proportion of active smokers among patients with hidradenitis suppurativa can be expressed by an odds ratio of 9.4, the calculated 95% confidence interval 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 history of hidradenitis suppurativa whereas 27% reported at least one affected first-degree relative.
CONCLUSION: From the exceedingly high rate of smokers among patients with this condition we conclude that cigarette smoking is a major triggering factor of hidradenitis suppurativa. Remarkably, the disease can be categorized as a smoking sequel that is neither of vascular nor neoplastic nature. Because familial occurrence was rather rarely reported, and because an environmental factor in the form of cigarette smoking appears to be of crucial importance to trigger the disease, we assume that the genetic basis of hidradenitis suppurativa is polygenic rather than mendelian. Smoking cessation should be encouraged particularly in patients with hidradenitis suppurativa although it is unknown whether this improves the course of the disease.