When should a patient with hidradenitis suppurativa be referred for systemic therapy rather than just topical or oral antibiotics?

If lesions persist beyond 2–3 weeks despite a full course of oral antibiotics, or if there are multiple interconnected tunnels (sinus tracts), widespread involvement, or significant pain affecting daily activities, systemic options such as biologics (e.g., adalimumab) are recommended. Referral to a dermatologist experienced in HS is appropriate at that point.

What lifestyle changes can reduce the frequency of flare‑ups in hidradenitis suppurativa?

Weight loss (if overweight), smoking cessation, and wearing loose‑fitting, breathable clothing can lower friction and moisture that trigger lesions. Regular gentle cleansing with a mild antiseptic wash, and using topical clindamycin or benzoyl peroxide during early nodules, may also help.

What warning signs indicate that an HS lesion might be becoming cancerous, and what should be done?

lesion that enlarges rapidly, becomes ulcerated, bleeds persistently, or fails to heal despite appropriate treatment should raise suspicion for squamous cell carcinoma, especially in long‑standing buttock or perianal disease. Prompt biopsy by a dermatologist or surgeon is essential, followed by oncologic management if malignancy is confirmed.

How are chronic sinus tracts and scarring managed surgically, and what are the risks?

Surgical options include incision and drainage for acute abscesses, limited excision of individual tunnels, or wide excision with skin grafting for extensive disease. Risks include wound infection, delayed healing, and recurrence if not all diseased tissue is removed. Post‑operative wound care and continued medical therapy reduce these risks.

Hidradenitis suppurativa

Hidradenitis suppurativa is a chronic inflammatory skin disease marked by painful, recurrent nodules that can scar and affect up to 1 % of the population, especially women.

Overview

Hidradenitis suppurativa, also known as acne inversa, is a chronic skin disease characterized by recurrent boil‑like lumps (nodules) under the skin. The nodules become inflamed and painful. They tend to break open (rupture), causing abscesses that drain fluid and pus. As the abscesses heal, they produce significant scarring of the skin.

The signs and symptoms typically appear after puberty, usually in a person's teens or twenties, although they can begin earlier, particularly in affected females. Nodules are most likely to form in the armpits and groin. They may also develop around the anus, on the buttocks, or under the breasts. In some cases, nodules appear in other areas, such as the nape of the neck, waist, and inner thighs.

The recurrent nodules and abscesses cause chronic pain and can lead to self‑consciousness, social isolation, and depression. Rarely, long‑term (chronic) abscesses on the buttocks can develop into a type of skin cancer.

Frequency

Hidradenitis suppurativa was once thought to be a rare condition because only the most severe cases were reported. However, recent studies have shown that the condition affects at least 1 in 100 people when milder cases are also considered. For reasons that are unclear, women are more commonly affected than men.

Causes

Pathophysiology

In most cases, the cause is unknown. The condition probably results from a combination of genetic and environmental factors. Originally, researchers believed that the disorder was caused by the blockage (occlusion) of specialized sweat glands called apocrine glands. Recent studies have shown that the condition actually begins with a blockage of hair follicles in areas of the body that also contain a high concentration of apocrine glands (such as the armpits and groin). The hair follicles have a buildup of a fibrous protein called keratin (hyperkeratosis). The blocked follicles trap bacteria, leading to inflammation and rupture.

Genetic Factors

Genetic factors clearly play a role. Some cases have been found to result from variants (mutations) in the NCSTN, PSEN1, or PSENEN gene. The proteins produced from these genes are components of the γ‑secretase complex, which cleaves many different proteins and is essential for several signaling pathways. One of these pathways, Notch signaling, is crucial for normal growth and differentiation of hair‑follicle cells and other skin cells, as well as for normal immune function. Variants in the mentioned genes impair Notch signaling, promoting nodule development and skin inflammation. Researchers are investigating whether additional genes encoding other γ‑secretase components are also associated.

Risk Factors

Obesity and smoking both appear to increase the risk of the disorder, and obesity is also associated with increased severity of signs and symptoms. Studies suggest that neither abnormal immune system function nor hormonal factors play a key role. Factors mistakenly thought to be associated include poor hygiene, the use of under‑arm deodorants and antiperspirants, and shaving or the use of depilatory products.

Inheritance

Hidradenitis suppurativa has been reported to run in families. Studies have found that 30 to 40 percent of affected individuals have at least one family member with the disorder, though this may be an underestimate because of nondisclosure or misdiagnosis.

In some families, including those with an NCSTN, PSEN1, or PSENEN gene variant, hidradenitis suppurativa appears to have an autosomal dominant pattern of inheritance, meaning one copy of an altered gene in each cell is sufficient to cause the disorder. In many cases, an affected person inherits the altered gene from a parent who has the condition.

Other Names

Acne inversa
Apocrinitis
Hidradenitides, suppurative
Hidradenitis, suppurative
Suppurative hidradenitides
Suppurative hidradenitis

Additional Information & Resources

Genetic Testing Information

Genetic Testing Registry: Familial acne inversa

Patient Support and Advocacy Resources

National Organization for Rare Disorders (NORD)

Clinical Trials

ClinicalTrials.gov

Catalog of Genes and Diseases from OMIM

ACNE INVERSA, FAMILIAL, 1; ACNINV1
ACNE INVERSA, FAMILIAL, 2, WITH OR WITHOUT DOWLING‑DEGOS DISEASE; ACNINV2
ACNE INVERSA, FAMILIAL, 3; ACNINV3

Scientific Articles on PubMed

PubMed

References

Alikhan A, Lynch PJ, Eisen DB. Hidradenitis suppurativa: a comprehensive review. J Am Acad Dermatol. 2009 Apr;60(4):539-61; quiz 562-3. doi:10.1016/j.jaad.2008.11.911.
Canoui‑Poitrine F, Revuz JE, Wolkenstein P, et al. Clinical characteristics of a series of 302 French patients with hidradenitis suppurativa, with an analysis of factors associated with disease severity. J Am Acad Dermatol. 2009 Jul;61(1):51-7. doi:10.1016/j.jaad.2009.02.013.
Danby FW, Margesson LJ. Hidradenitis suppurativa. Dermatol Clin. 2010 Oct;28(4):779-93. doi:10.1016/j.det.2010.07.003.
Melnik BC, Plewig G. Impaired Notch signalling: the unifying mechanism explaining the pathogenesis of hidradenitis suppurativa (acne inversa). Br J Dermatol. 2013 Apr;168(4):876-8. doi:10.1111/bjd.12068.
Pink AE, Simpson MA, Desai N, et al. Mutations in the gamma‑secretase genes NCSTN, PSENEN, and PSEN1 underlie rare forms of hidradenitis suppurativa (acne inversa). J Invest Dermatol. 2012 Oct;132(10):2459-61. doi:10.1038/jid.2012.162.
Pink AE, Simpson MA, Desai N, et al. gamma‑Secretase mutations in hidradenitis suppurativa: new insights into disease pathogenesis. J Invest Dermatol. 2013 Mar;133(3):601-7. doi:10.1038/jid.2012.372.
Revuz J. Hidradenitis suppurativa. J Eur Acad Dermatol Venereol. 2009 Sep;23(9):985-98. doi:10.1111/j.1468-3083.2009.03356.x.
Revuz JE, Canoui‑Poitrine F, Wolkenstein P, et al. Prevalence and factors associated with hidradenitis suppurativa: results from two case‑control studies. J Am Acad Dermatol. 2008 Oct;59(4):596-601. doi:10.1016/j.jaad.2008.06.020.
Rosi E, Fastame MT, Scandagli I, et al. Insights into the Pathogenesis of HS and Therapeutical Approaches. Biomedicines. 2021 Sep 6;9(9):1168. doi:10.3390/biomedicines9091168.
Wang B, Yang W, Wen W, et al. Gamma‑secretase gene mutations in familial acne inversa. Science. 2010 Nov 19;330(6007):1065. doi:10.1126/science.1196284.