The epidemiology of hidradenitis suppurativa

Summary Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease defined clinically by multiple, painful inflammatory lesions occurring predominantly in flexural sites. Onset is typically soon after puberty; however, it remains unknown whether the menopause induces remission. In North American and European patients with HS the female‐to‐male ratio is approximately 3 : 1 but the ratio is 1 : 2 in South Korean patients. It may be that some elements of HS epidemiology cannot be generalized across all populations. Elements of HS epidemiology in the USA and Europe are well established, including strong associations with obesity and smoking, which may increase disease severity. There are associations between HS and other cardiovascular disease (CVD) risk factors, including type 2 diabetes and metabolic syndrome. People with HS have double the risk of death from CVD compared with those without HS and 1·5 times the risk compared with patients with psoriasis. Depression and anxiety are associated with HS and completed suicide rates in those with HS are more than double the rates in controls. Associations exist between HS and other chronic inflammatory conditions, particularly inflammatory bowel disease and inflammatory arthritis. Case–control studies demonstrate associations with pilonidal sinus, polycystic ovary syndrome, Down syndrome, obstructive sleep apnoea and pyoderma gangrenosum. Population‐based studies using routinely collected healthcare data from the USA estimate a prevalence of 0·1%, suggesting HS is relatively uncommon. European studies include undiagnosed patients and typically estimate prevalence of 1% or more, suggesting a common condition. Resolving the controversy surrounding a greater than 10‐fold difference in HS prevalence estimates remains a high priority. What is already known about this topic? •Hidradenitis suppurativa (HS) prevalence figures vary more than 80‐fold, from 0.05% to 4.1%. •In North America and Europe, HS is most prevalent in adult women of working age. •HS is linked to smoking and obesity. What does this study add? •Wide variation in HS prevalence estimates is probably due to differing data sources, different levels of recognition of HS and variable inclusion of undiagnosed cases. •HS is associated with other chronic inflammatory diseases, cardiovascular disease (CVD) and depression. •Mortality rates from CVD are more than 50% higher in HS than in psoriasis and there is an increased risk of completed suicide compar