Prevalence and Clinical Characteristics of Hidradenitis Suppurativa Phenotypes in a Large Dutch Cohort.

Dear Editor, Hidradenitis suppurativa (HS) is a chronic, recurrent, debilitating inflammatory skin disease. It has a heterogeneous clinical presentation regardless of disease severity [1]. Therefore, different phenotypes are thought to exist which might differ in their pathogenesis and prognosis and which will likely benefit from different treatment modalities. Based on clinical experience, a set of six phenotypes has been proposed in this journal: regular, frictional furunculoid, scarring folliculitis, conglobata, ectopic and syndromic [2]. However, our continued clinical experience suggested that the ectopic and syndromic types do not have specific clinical features and could be categorized as one of the other phenotypes. Here, we present the prevalence and patient characteristics of these phenotypes in a population of 935 Dutch HS patients participating in our HS registry at the Department of Dermatology of the Erasmus University Medical Center and its affiliated DermaHaven. All patients included in the study were diagnosed with HS according to the criteria of the European S1 guideline [3]. To help the phenotype designation in daily practice, we included a flowchart (Fig. 1) and prototypical clinical pictures of the phenotypes (available at www.karger.com/doi/10.1159/000518965). The need for ethical approval was waived by the Medical Research Eth-