Hidradenitis suppurativa (HS), sometimes known as acne inversa or Verneuil's disease, is a long-term dermatological condition characterized by the occurrence of inflamed and swollen lumps. These are typically painful and break open, releasing fluid or pus. The areas most commonly affected are the underarms, under the breasts, perineum, buttocks, and the groin. Scar tissue remains after healing. HS may significantly limit many everyday activities, for instance, walking, hugging, moving, and sitting down. Sitting disability may occur in patients with lesions in the sacral, gluteal, perineal, femoral, groin or genital regions. Prolonged periods of sitting down can also worsen the condition of the skin of these patients. The exact cause is usually unclear but believed to involve a combination of genetic and environmental factors. About a third of people with the disease have an affected family member. Other risk factors include obesity and smoking. The condition is not caused by an infection, poor hygiene, or the use of deodorant. Instead, it is believed to be caused by hair follicles being obstructed, with the nearby apocrine sweat glands being strongly implicated in this obstruction. The sweat glands may or may not be inflamed. Diagnosis is based on the symptoms. No cure is known, though surgical excision with wet-to-dry dressings, proper wound care, and warm baths or showering with a pulse-jet shower may be used in those with mild disease. Cutting open the lesions to allow them to drain does not result in significant benefit. While antibiotics are commonly used, evidence for their use is poor. Immunosuppressive medication may also be tried. In those with more severe disease, laser therapy or surgery to remove the affected skin may be viable. Rarely, a skin lesion may develop into skin cancer. If mild cases of HS are included, then the estimate of its frequency is from 1–4% of the population. Women are three times more likely to be diagnosed with it than men. Onset is typically in young adulthood and may become less common after 50 years old. It was first described between 1833 and 1839 by French anatomist Alfred Velpeau.
Terminology Although hidradenitis suppurativa is often called acne inversa, it is not a form of acne. Hidradenitis suppurativa lacks the core defining features of acne, such as the presence of closed comedones and increased sebum production.
Causes The exact cause of hidradenitis suppurativa remains unknown, and there has, in the recent past, been notable disagreement among experts in this regard. The condition, however, likely stems from both genetic and environmental causes. Specifically, an immune-mediated pathology has been proposed, although environmental factors have not been ruled out. Lesions will occur in any body area with hair follicles, and/or sweat glands. Areas such as the axilla, groin, and perineal region are more commonly involved. This theory includes most of these potential indicators:
Post-pubescent individuals Blocked hair follicles or blocked apocrine sweat glands Excessive sweating Androgen dysfunction Genetic disorders that alter cell structure The historical understanding of the disease suggests dysfunctional apocrine glands or dysfunctional hair follicles, possibly triggered by a blocked gland, which creates inflammation, pain, and a swollen lesion.
Triggering factors Several triggering factors should be taken into consideration:
Obesity is an exacerbating rather than a triggering factor, through mechanical irritation, occlusion, and skin maceration. Tight clothing, and clothing made of heavy, non-breathable materials Deodorants, depilation products, shaving of the affected area – their association with HS is still an ongoing debate among researchers. Drugs, in particular oral contraceptive pills, cigarette smoking, and lithium. Hot and especially humid climates. Stress
Predisposing factors Genetic factors: an autosomal dominant inheritance pattern has been proposed. Endocrine factors: Sex hormones, especially an excess of androgens, are thought to be involved, although the apocrine glands are not sensitive to these hormones. Women often have outbreaks before their menstrual period and after pregnancy; HS severity usually decreases during pregnancy and after menopause. Diabetes mellitus is common in hidradenitis suppurativa and seems to be a risk factor. Some cases have been found to result from mutations in the NCSTN, PSEN1, or PSENEN genes. The genes produce proteins that are all components of a complex called gamma- (γ-) secretase. This complex cuts apart (cleaves) many different proteins, which is a crucial step in several chemical signaling pathways. One of these pathways, known as notch signaling, is essential for the normal maturation and division of hair follicle cells and other types of skin cells. Notch signaling influences normal immune system function. Studies suggest mutations in the NCSTN, PSEN1, or PSENEN genes impair notch signaling in hair follicles. Although little is known about the mechanism, abnormal notch signaling appears to promote the development of nodules and lead to skin inflammation. In addition, the composition of the intestinal microflora and as a consequence dietary patterns appear to play a role. Although dysbiosis of the cutaneous microbiome, apparent in HS, is not observed, the concurrent presence of inflammatory gut and skin diseases has led to the hypothesis of a gut-skin axis in which gut microbiota is implicated. Indeed, analysis of bacterial taxa in fecal samples from HS patients supports the possibility of a role for intestinal microbial alterations in this chronic inflammatory skin disease. Hidradenitis suppurativa has also been discussed as a possible manifestation of some inborn errors of immunity. A 2026 review noted overlap between HS pathogenesis and monogenic disorders affecting epithelial–innate immune interactions, Th17 differentiation, neutrophil function, and inflammasome regulation, including STAT3-associated hyper-IgE syndrome, STAT1 gain-of-function disease, chronic granulomatous disease, and selected autoinflammatory syndromes.
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