Hidradenitis Suppurativa (HS) Overview

HS, sometimes referred to as acne inversa, is a chronic, noncontagious inflammatory disease that is characterized by painful, inflamed lumps beneath the skin. These lesions often develop in areas where skin rubs together, such as the armpits, groin, upper thighs, or buttocks, and they may rupture and drain fluid. Chronic inflammation and abscess formation can lead to scarring, tunneling beneath the skin, and chronic drainages.^{1 , 2} The condition often leads to chronic pain.¹ In rare cases, long-standing chronic abscesses in areas such as the buttocks can progress to squamous cell carcinoma.^{1 , 2} Beyond its physical manifestations, HS can affect a person's psychosocial well-being, contributing to self-consciousness, social isolation, and symptoms of depression.^{1 - 3}

HS is thought to begin with the blockage of hair follicles, most often in areas with a high concentration of apocrine glands, such as the armpits or groin.¹ Though the underlying cause of this blockage is unknown, a combination of genetic, environmental, and hormonal factors may play a role. The condition may run in families, with studies suggesting that 30 to 40 percent of affected individuals have at least one family member with HS; however, this figure is likely an underestimate because the condition itself is often underdiagnosed or underreported.^{1 , 4} Research indicates that genetic variants may disrupt cell signaling pathways that are important for normal hair follicle growth and immune function, potentially contributing to the development of the condition.¹ Smoking and obesity may also be associated with an increased risk for HS, and obesity has been linked to greater severity of signs and symptoms in affected individuals.¹

HS is more common in Black individuals, and it disproportionally impacts women, affecting approximately three women for every man.^{2 , 4} Though the reason for this difference is not fully understood, hormonal influences are thought to play a role.² The condition most commonly develops after puberty, in the teens or twenties, and earlier onset has been reported more frequently in females.^{1 - 4} In addition, clinical observations suggest that symptoms may fluctuate with the menstrual cycle and during periods of hormonal change, including puberty and menopause, as well as with exogenous hormone use.²

HS is diagnosed clinically based on characteristic signs and symptoms. It is characterized as mild (one to a few lumps in one area), moderate (recurring lumps, abscesses in more than one area), or severe (widespread lumps, scarring, and chronic pain).^{2 , 3} Although there are currently no validated biological or pathological tests that can diagnose the condition, laboratory tests of the lesions can rule out other conditions. Treatment for HS is highly individualized and may vary based on the severity of the condition. Three biologics (adalimumab, bimekizumab, and secukinumab) are approved for treating moderate to severe HS.⁵ Other treatment options typically include topical and systemic antibiotics, corticosteroids, retinoids, hormone therapy, and immune modulators.^{2 - 4} Surgery may also be used to "de-roof” lesions (remove the tops of lesions) or, in advanced cases, to remove larger areas of affected tissue.^{2 , 4}

The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) is the primary organization for research on HS at NIH. Current research aims to better understand the underlying causes of HS, including its genetic, immune, and environmental contributors, while identifying effective medical and surgical treatments to improve symptoms and quality of life.⁴

The NIAMS Systemic Autoimmunity Branch has produced studies that examine immune mechanisms in people with HS, including studies on the inflammatory processes that drive disease development.⁶ NIAMS has also included HS in its pain research portfolio, as pain is one of the most disabling and poorly managed aspects of the disease. A 2023 NIAMS-funded pain research grant supported a study that focused on understanding HS-related pain in adolescents and developing strategies to reduce pain and prevent long-term opioid use.⁷

Ongoing research continues to deepen our understanding of HS to inform future treatment approaches. For example, one NIAMS-supported project is examining how changes in skin microbes and immune responses contribute to disease development, with the goal of identifying biological targets for future therapies.⁸