The present invention relates to methods of determining the clinical phenotype of patients suffering from hidradenitis suppurativa (HS), a chronic inflammatory skin disease characterized by recurrent nodules, abscesses, and sinus tracts in the intertriginous areas. The invention is based on the discovery of a set of biomarkers that are differentially expressed in the hairfollicles of HS patients. The invention provides methods of measuring the levels of these biomarkers in biological samples from HS patients, and using them to classify the patients into different phenotypic groups. The invention also provides methods of selecting or adjusting the treatment for HS patients based on their phenotypic group. The invention thus offers a novel and useful tool for the personalized diagnosis and management of HS.