Hidradenitis Suppurativa

Written by Dr Síona Ní Raghallaigh, Consultant Dermatologist in Beaumont and Bon Secours Hospitals and Dr Marta Costa Blasco, Dermatology Registrar in Beaumont Hospital

Introduction

Hidradenitis suppurativa (HS) is a chronic inflammatory skin disorder mainly affecting intertriginous sites such as the axillary, inguinal, anogenital and infra-mammary areas. It is characterised by recurrent abscesses and painful nodules that can lead to sinus tract formation and scarring. Previously thought to be a suppurative disorder of the apocrine glands (hence its misnomer), it is now understood to be a chronic follicular occlusive disease involving the follicular portion of the pilosebaceous unit. The management of Hidradenitis Suppurativa is multifactorial, involving both medical and surgical interventions, in addition to pain control, wound care advice, lifestyle modification and psychological support. Hidradenitis Suppurativa can have a significant negative impact on quality of life. 1,2

Epidemiology

The estimated prevalence in a recent large European study is 0.7 -1.2 %. Women are more likely to develop HS than men, with a sex ratio of 3.6:1. The average age of affected individuals is 24. The duration of disease is approximately 25 years, with a diagnostic delay of 7 years. 3,4

Pathogenesis

The initial pathogenic event consists of follicular hyperkeratosis and plugging, leading to follicular dilation and rupture, with subsequent inflammation and sinus formation. HS is initially a sterile process, but bacterial biofilm alterations may contribute to the persistence of inflammation. 1,2,5 Dysregulation of the innate and adaptive immune systems likely play a role in HS. Cytokine levels are abnormal in HS patients, with elevation of IL1β, IL-17 and TNFα. 6 Although HS is rare in prepubertal children, and a subset of female HS patients experience pre-menstrual flares, no evidence of biochemical hyperandrogenism has been demonstrated. 1 A body mass index ≥30 has been shown to be present in 21% of patients with HS versus only 9% of controls 7 and obesity correlates with disease severity. 15% weight loss can lead to a 30% improvement in disease. There is a strong relationship between smoking and HS. In a case-control study of 302 patients with HS and 906 controls, 76% of HS patients versus 25% of controls were current smokers. 8 A family history of HS is noted in a third of the patients. Mutations in the gamma secretase complex may play a role in these instances. 9

Clinical features

Dessau criteria 10 is used for the diagnosis of HS:

  1. Characteristic lesions: deep-seated painful nodules that can progress to abscess formation and draining sinuses, leading to bridged scars; presence of double-ended pseudo-comedones.
  2. Typical distribution: lesions are usually found in axillae, inframammary folds, inner upper thighs, and anogenital region
  3. Relapses and chronicity

There are several phenotypes; the most typically seen has an axillary-mammary predominance and occurs more often in women. Lesions are also present in the inguinal and gluteal area. The follicular variant is more common in males and smokers. Pilonidal sinuses and severe acne may be observed in this variant. It usually involves other sites such as ears, chest, trunk and lower limbs. The third variant predominantly affects the gluteal region, and it is also more commonly seen in men. 11

Severity is assessed using the Hurley classification. It comprises the following stages:

  1. Recurrent isolated abscess formation; sinus tracts and scarring are not seen
  2. Recurrent abscesses with sinus tract formation
  3. Diffuse involvement of an area with multiple interconnecting sinus tracts. 1,2

Another tool to record severity is the Sartorius Hidradenitis Suppurativa Score, which is obtained by counting involved regions, nodules and sinus tracts. 12

Complications

Super-infection is a common complication which can lead to osteomyelitis. Severe disease can cause lymphatic obstruction leading to lymphoedema. Strictures and contractures can occur. Fistula formation (involving the gastrointestinal or genitourinary tracts) can develop. The prevalence of pyoderma gangrenosum is known to be higher in HS compared to the general population. Chronic inflammation can lead to anaemia, hypoproteinemia, and amyloidosis. Squamous cell carcinoma can rarely develop in skin affected by HS after many years of disease. 13

Treatment

The management of HS should be individualised. General measures include psychosocial support, active weight management in overweight or obese patients, smoking cessation, pain management and practical advice on loose-fitting clothes and dressings. For acutely symptomatic lesions, warm compresses may help. Intralesional corticosteroid injections and punch debridement (partial deroofing) are also commonly used. Incision and drainage should be limited to situations in which immediate relief of severe pain from an inflamed, fluctuant nodule is necessary. 1,2

The treatment for mild disease generally starts with topical therapy such as clindamycin 1% twice daily for 12 weeks. Despite their common use, the evidence for topical antiseptics such as chlorhexidine preparations remains lacking. 14

Oral tetracyclines, given both for their bacteriostatic and anti-inflammatory effect, are normally prescribed initially for 12 – 16 weeks with assessment of response. Commonly used options are lymecycline 408 mg daily or doxycycline 100 mg twice daily. In Hurley stages II and III, clindamycin 300 mg combined with rifampicin 300 mg twice daily for 10 weeks are widely used. Intravenous carbapenems are sometimes utilized as rescue treatments for severe superimposed infections. 15

Oral antiandrogenic therapy can be helpful, especially in patients that report a perimenstrual flare. Spironolactone escalated to 100 mg daily has shown benefit at 3 months of treatment. Antiandrogenic oral contraceptive treatments are also a therapeutic option. 16

Metformin has shown benefit in several case series. The mechanism of action is unknown, but it is thought it might be due its anti-androgen and antinflammatory effect. It may also lead to mild weight loss. 17

Retinoids are also part of the treatment of HS. Acitretin has antiproliferative effects on keratinocytes. The doses required range from 50 to 75 mg per day. 18

Anti-TNF agents are used for more severe disease. Large studies have shown approximately a 60% improvement in symptoms. Adalimumab is licensed in higher doses than normally prescribed for other skin conditions. It is administered subcutaneously and maintained at 40 mg weekly after an initial loading dose. Infliximab is less often used. 19

Ustekinumab, an IL12/23- inhibitor, has been shown to lead to disease improvement in 35 – 45% of patients in 2 small studies. (ref) Additional agents for which benefit has been suggested include anakinra, secukinumab, guselkumab, canakinumab, as well as ertapenem, cyclosporine, apremilast and oral tacrolimus. 20,21

Sinus tracts typically require surgical intervention for resolution. Surgical deroofing involves removal of skin overlying sinus tracts or nodules, followed by healing by secondary intention. Wide excision with or without skin grafting is also performed.

In summary, hidradenitis suppurativa is a chronic relapsing condition that requires a multidisciplinary approach with a focus on treating skin disease, comorbidities and managing the psychosocial aspect of the condition.

References available on request

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