Hidradenitis suppurativa

Several triggering factors should be taken into consideration:

• Obesity[19] is an exacerbating rather than a triggering factor,[20] through mechanical irritation, occlusion, and skin maceration.
• Tight clothing,[19] and clothing made of heavy, nonbreathable materials[21]
• Deodorants, depilation products, shaving of the affected area – their association with HS is still an ongoing debate among researchers.[22]
• Drugs, in particular oral contraceptive pills[23] and lithium.[24]
• Hot and especially humid climates.[25]

• Genetic factors:[20] an autosomal dominant inheritance pattern has been proposed.[26]
• Endocrine factors: sex hormones, especially an excess of androgens, are thought to be involved, although the apocrine glands are not sensitive to these hormones.[27] Women often have outbreaks before their menstrual period and after pregnancy; HS severity usually decreases during pregnancy and after menopause.

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 an important 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 is also involved in normal immune system function. Studies suggest that mutations in the NCSTN, PSEN1, or PSENEN gene impair notch signaling in hair follicles. Although little is known about the mechanism, abnormal notch signaling appears to promote the development of nodules and to lead to inflammation in the skin.[28] 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 existence of inflammatory gut and skin diseases has led to the postulation of a gut-skin axis in which gut microbiota is implicated. Indeed, analysis of bacterial taxa in fecal samples from HS patients support the possibility of a role for intestinal microbial alterations in this chronic inflammatory skin disease.[29]

A case of hidradenitis suppurativa

Micrograph of hidradenitis suppurativa: Sinus tracts [(A), arrow], active inflammation, and rupture [(B), asterisks] of the follicular epithelium with “floating” hair fragments [(B), arrow]. Subsequently, a secondary inflammatory response is induced with influx of numerous neutrophils [(C), arrows] and granulomatous foreign body reaction with giant cells [(C), asterisks].[30]

Hidradenitis suppurativa presents itself in three stages.[17][31] Due to the large spectrum of clinical severity and the severe impact on quality of life, a reliable method for evaluating HS severity is needed.

Hurley's staging system was the first classification system proposed, and is still in use for the classification of patients with skin diseases (i.e., psoriasis, HS, acne). Hurley separated patients into three groups based largely on the presence and extent of cicatrization and sinuses. It has been used as a basis for clinical trials in the past and is a useful basis to approach therapy for patients. These three stages are based on Hurley's staging system, which is simple and relies on the subjective extent of the diseased tissue the patient has. Hurley's three stages of hidradenitis suppurativa are:[32]

The Sartorius staging system is more sophisticated than Hurley's. Sartorius et al. suggested that the Hurley system is not sophisticated enough to assess treatment effects in clinical trials during research. This classification allows for better dynamic monitoring of the disease severity in individual patients. The elements of this staging system are:[33]

• Anatomic regions involved (axilla, groin gluteal, or other region or inframammary region left or right)
• Number and types of lesions involved (abscesses, nodules, fistulas or sinuses, scars, points for lesions of all regions involved)
• The distance between lesions, in particular the longest distance between two relevant lesions (i.e., nodules and fistulas in each region or size if only one lesion present)
• The presence of normal skin in between lesions (i.e., if all lesions are clearly separated by normal skin)

Points are accumulated in each of the above categories, and added to give both a regional and total score. In addition, the authors recommend adding a visual analog scale for pain or using the dermatology life quality index (DLQI, or the 'skindex') when assessing HS.[34]

Warm baths may be tried in those with mild disease.[4] Weight loss and the cessation of smoking are also recommended.[2]

• Antibiotics: taken by mouth, these are used for their anti-inflammatory properties rather than to treat infection. Most effective is a combination of rifampicin and clindamycin given concurrently for 2–3 months. Popular antibiotics also include tetracycline and minocycline.[36] Topical clindamycin has been shown to have an effect in double-blind placebo controlled studies.[37]
• Corticosteroid injections, also known as intralesional steroids, can be particularly useful for localized disease, if the drug can be prevented from escaping via the sinuses.
• Antiandrogen therapy, hormonal therapy with antiandrogenic medications such as spironolactone, flutamide, cyproterone acetate, ethinylestradiol, finasteride, dutasteride, and metformin, have been found to be effective in clinical studies.[38][39][40] However, the quality of available evidence is low and does not presently allow for robust evidence-based recommendations.[38][39]
• Intravenous infusion or subcutaneous injection of anti-inflammatory (TNF inhibitors; anti-TNF-alpha) drugs such as infliximab, and etanercept[41] This use of these drugs is not currently Food and Drug Administration (FDA) approved and is somewhat controversial, so may not be covered by insurance.
• TNF inhibitor: Studies have supported that various TNF inhibitors have a positive effect on HS lesions.[42] Specifically adalimumab at weekly intervals is useful.[43] Adalimumab is the only medication approved by the FDA for the treatment of HS as of 2021.
• Topical isotretinoin is usually ineffective in people with HS, and is more commonly known as a medication for the treatment of acne vulgaris. Individuals affected by HS who responded to isotretinoin treatment tended to have milder cases of the condition.[44]

When the process becomes chronic, wide surgical excision is the procedure of choice. Wounds in the affected area do not heal by secondary intention, and immediate or delayed application of a split-thickness skin graft is an option.[15] Another option is covering the defect with a perforator flap. With this technique, the (mostly totally excised) defect is covered with tissue from an area nearby. For example, the axilla with a fully excised defect of 15 × 7 cm can be covered with a thoracodorsal artery perforator flap.

The 1064-nm wavelength laser for hair removal may aid in the treatment of HS.[45] A randomized control study has shown improvement in HS lesions with the use of an Nd:YAG laser.[46]

• Contractures and reduced mobility of the lower limbs and axillae due to fibrosis and scarring occur. Severe lymphedema may develop in the lower limbs.
• Local and systemic infections (meningitis, bronchitis, pneumonia, etc.), are seen, which may even progress to sepsis.
• Interstitial keratitis
• Anal, rectal, or urethral fistulae[49]
• Normochromic or hypochromic anemia[50]
• People with HS may be at increased risk for autoimmune disorders including ankylosing spondylitis, rheumatoid arthritis, and psoriatic arthritis.[51]
• Squamous cell carcinoma has been found on rare occasions in chronic hidradenitis suppurativa of the anogenital region.[52] The mean time to the onset of this type of lesion is 10 years or more and the tumors are usually highly aggressive.
• Tumors of the lung and oral cavity, and liver cancer[53]
• Hypoproteinemia and amyloidosis, which can lead to kidney failure and death[54]
• Seronegative and usually asymmetric arthropathy: pauciarticular arthritis, polyarthritis/polyarthralgia syndrome[55]

Hidradenitis suppurativa has been referred to by multiple names in the literature, as well as in various cultures. Some of these are also used to describe different diseases, or specific instances of this disease.[31]

• Acne conglobata – not really a synonym – this is a similar process, but in classic acne areas of chest and back
• Acne inversa – a proposed new term[63][64] which has not gained widespread favor.[65]
• Apocrine acne – an outdated term based on the disproven concept that apocrine glands are primarily involved, though many do have apocrine gland infection
• Apocrinitis – another outdated term based on the same thesis
• Fox-den disease – a term not used in medical literature, based on the deep fox den–like sinuses
• Hidradenitis supportiva – a misspelling
• Pyodermia fistulans significa – now considered archaic
• Verneuil's disease – recognizing the surgeon whose name is most often associated with the disorder as a result of his 1854–1865 studies[66]