Hidradenitis suppurativa: an update on epidemiology, phenotypes, diagnosis, pathogenesis, comorbidities and quality of life

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease that severely impairs patients' quality of life. It is characterized by recurrent painful nodules, abscesses and draining sinus tracts in primarily intertriginous areas. We aimed to review the most up-to-date information regarding the epidemiology, clinical presentation, diagnostic studies, pathogenesis, comorbidities and quality of life of patients with hidradenitis suppurativa. We performed a systematic search of Medline, Embase database (from inception to September 2019) and review of bibliographies without restrictions on year or language. HS has an estimated global prevalence of 0.00033-4.1% (but most likely 0.7-1.2% in the European-US population). Patients still experience a significant diagnostic delay, up to several years. In the absence of pathognomonic tests, the diagnosis of HS is made from clinical observation and the disease narrative. Phenotypic variation renders diagnosis and severity assessment difficult. Ultrasound imaging is an emerging assessment tool for deep-seated lesions. The Hurley Staging System is still widely used in severity rating. Follicular hyperkeratosis and dilatation, follicular rupture and chronic inflammation with architectural tissue changes have been implicated in the pathogenesis of HS. HS has been associated with metabolic syndrome and other risk factors for cardiovascular disease, diabetes mellitus type II, polycystic ovarian syndrome, depression, suicide and substance use disorders. It has been linked to other immune-mediated diseases such as inflammatory bowel disease and spondyloarthropathy. Pain, pruritus, malodour, low self-esteem, sleep and sexual dysfunctions, and poor mental health are chronic symptoms or consequences of uncontrolled disease. HS is an under-diagnosed and under-treated disease with a profound negative impact on patients' quality of life. In the light of its associated comorbidities, an interdisciplinary management approach may be needed to ensure the best outcomes.