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Hidradenitis Suppurativa

What Is It, Causes, Presentation and More

Author:Nikol Natalia Armata, MD

Editors:Alyssa Haag,Ian Mannarino, MD, MBA,Kelsey LaFayette, DNP, ARNP, FNP-C

Illustrator:Jessica Reynolds, MS

Copyeditor:Stacy Johnson, LMSW


What is hidradenitis suppurativa?

Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic inflammatory skin condition characterized by subcutaneous nodules (i.e., located in the deep dermis and subcutis), abscesses, draining tracts (i.e., sinus tracts), and fibrotic scars. These lesions most commonly occur in sites where opposing skin surfaces come into contact while at rest and areas rich in apocrine glands (e.g., sweat glands). Increasing knowledge of its pathogenesis has led to the prevailing theory that it is a chronic follicular occlusive disease involving the follicular portion of folliculopilosebaceous units (i.e., hair follicle and sebaceous glands).

Shading of areas common to have hidradenitis suppurative.

What causes hidradenitis suppurativa?

Hidradenitis suppurativa results from dysfunctional hair follicles and apocrine sweat glands that lead to pore clogging, inflammation, and painful abscesses. Hair follicles usually build up with a fibrous protein called keratin (i.e., hyperkeratosis) due to excessive pressure, inflammation, irritation of the skin, or genetics. Once blocked by excessive keratin, hair follicles trap bacteria, leading to inflammation and rupture. Nonetheless, the underlying causes that can lead to hidradenitis suppurativa can be environmental or genetic. Friction from clothes and hormonal changes, sweating, or humidity can trigger the formation of hidradenitis suppurativa. Genetic causes include apocrine gland dysfunction and variations of several chemical signaling pathways (e.g., the Notch signaling pathway, which is essential for the growth and differentiation of hair follicles). Finally, obesity, tight clothes, smoking, excessive deodorant use, and shaving all increase the risk of hidradenitis suppurativa formation. 

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What are the signs and symptoms of hidradenitis suppurativa?

Hidradenitis suppurativa usually presents as red, inflamed, and painful bumps on the skin, most typically in the axilla, groin, and under the breasts. These lesions may also contain pus. Clinically, HS is characterized by the appearance of open double-headed comedones (i.e., blackheads); painful firm papules (i.e., raised area of skin tissue < 1 cm in diameter), and nodules (i.e., elevated, solid, palpable lesions > 1 cm in diameter); abscesses; as well as hypertrophic and atrophic scars. Of note, these lesions may also be found on the back, buttocks, and abdominal fold. 

How is hidradenitis suppurativa diagnosed?

The diagnosis of hidradenitis suppurativa is based on a thorough clinical examination and review of the individual's medical history. Certain aspects of the medical history can offer valuable information to guide the diagnosis, including the individual’s age, family history, and any risk factors. Physical examination typically involves assessing the size, shape, color, location, distribution, and duration. If any of the lesions are leaking, the clinician may take a swab of the fluid. 

Once diagnosed, the healthcare professional can determine the severity of each lesion based on Sartorius/Hurley’s staging systems.  Stage I involves solitary or multiple isolated abscesses without scarring or sinus tracts (i.e., blind-ended tunnels or cavities connecting to the skin or mucosal surface). Stage II consists of recurrent abscesses or lesions that may be single, multiple, or widely separated with sinus tract formation. Stage III includes diffuse, regional abscesses with numerous interconnected sinus tracts. 

How is hidradenitis suppurativa treated?

Management of hidradenitis suppurativa depends on the severity of the lesions and the underlying cause. Various measures may be recommended to reduce symptoms such as pain and drainage, speed up healing, and prevent further infection or scarring. Lifestyle changes like smoking cessation and weight loss may reduce the risk of HS formation. Additionally,  personalized skin care plans may be recommended and may include regular washing of the affected areas with water and soap, avoiding irritants like deodorants; and scheduling laser treatments for removing hair or older scarring can also be beneficial. 

Individuals with persistent HS that does not resolve with the conservative measures might require medications, like corticosteroid injections; anti-androgens (e.g., spironolactone); oral antibiotics (e.g., clindamycin); or tumor necrosis factor (TNF) inhibitor medications (i.e., adalimumab) to reduce inflammation. Resorcinol, an organic chemical compound known as benzenediol, may also be prescribed to open the clogged hair follicles and minimize the inflammation. Pain management is also critical,  and depending on the disease severity and type of pain, topical lidocaine, topical or systemic nonsteroidal anti-inflammatories, gabapentin, or serotonin-norepinephrine reuptake inhibitors may be beneficial. Due to the pain, sensitive location of lesions, scarring, drainage, and odor, the negative psychosocial impact of the disease should also be considered in treatment. Other treatment options include incision, drainage of the lesions, and surgical removal of any existing sinus tracts. 

What are the most important facts to know about hidradenitis suppurativa?

Hidradenitis suppurativa (HS) refers to a chronic inflammatory skin condition with subcutaneous nodules and abscesses, draining tracts, and fibrotic scars in areas of the body that usually contain a high concentration of apocrine glands (e.g., axilla, groin, and under the breasts). This condition usually results from a combination of genetic and environmental factors. The affected areas typically present as red, inflamed, and painful bumps on the skin, which may contain pus. The diagnosis is based on clinical examination and review of the individual's medical history, whereas management depends on the severity of the lesions and the underlying cause. Various measures may be recommended to reduce symptoms, expedite healing, and prevent further infection or scarring.

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Related links

Skin histology
Acneiform skin disorders: Pathology review
Skin and soft tissue inflammation and infections notes

Resources for research and reference

Ballard, K., Shuman, V.L. Hidradenitis Suppurativa. [Updated 2022 Jul 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK534867/ 

Hidradenitis Suppurativa. DermNet. (n.d.). Retrieved July 22, 2022, from https://dermnetnz.org/topics/hidradenitis-suppurativa

Hidradenitis suppurativa: Diagnosis and treatment. American Academy of Dermatology. (n.d.). Retrieved July 24, 2022, from https://www.aad.org/public/diseases/a-z/hidradenitis-suppurativa-treatment  

Skin and soft tissue inflammation and infections notes - osmosis. (n.d.). Retrieved July 20, 2022, from https://www.osmosis.org/notes/Skin_and_soft_tissue_inflammation_and_infections