What is hidradenitis suppurativa?
Hidradenitis suppurativa is an inflammatory skin disease that affects apocrine gland-bearing skin in the axillae, in the groin, and under the breasts. It is characterised by recurrent boil-like nodules and abscesses that culminate in pus-like discharge, difficult-to-heal open wounds (sinuses) and scarring.
The term hidradenitis implies it starts as an inflammatory disorder of sweat glands, which is now known to be incorrect. Hidradenitis suppurativa is also known as acne inversa.
Who gets hidradenitis suppurativa?
Hidradenitis often starts at puberty, and is most active between the ages of 20 and 40 years, and in women, can resolve at menopause. It is three times more common in females than in males. Risk factors include:
- Other family members with hidradenitis suppurativa
- Obesity and insulin resistance/metabolic syndrome
- Cigarette smoking
- Follicular occlusion disorders: acne conglobata, dissecting cellulitis, pilonidal sinus
- Inflammatory bowel disease (Crohn disease)
- Rare autoinflammatory syndromes associated with abnormalities of PSTPIP1 gene.*
* PAPA syndrome (pyogenic arthritis, pyoderma gangrenosum and acne), PASH syndrome (pyoderma gangrenosum, acne, suppurative hidradenitis) and PAPASH syndrome (pyogenic arthritis, pyoderma gangrenosum, acne, suppurative hidradenitis).
What causes hidradenitis suppurativa?
Hidradenitis suppurativa is an autoinflammatory disorder. Although the exact cause is not yet understood, contributing factors include:
- Friction from clothing and body folds
- Aberrant immune response to commensal bacteria
- Abnormal cutaneous or follicular microbiome
- Follicular occlusion
- Release of pro-inflammatory cytokines
- Inflammation causing rupture of the follicular wall and destroying apocrine glands and ducts
- Secondary bacterial infection
- Certain drugs.
What are the clinical features of hidradenitis suppurativa?
Hidradenitis can affect a single or multiple areas in the armpits, neck, submammary area, and inner thighs. Anogenital involvement most commonly affects the groin, mons pubis, vulva (in females), sides of the scrotum (in males), perineum, buttocks and perianal folds.
- Open and closed comedones
- Painful firm papules and larger nodules
- Pustules, fluctuant pseudocysts and abscesses
- Pyogenic granulomas
- Draining sinuses linking inflammatory lesions
- Hypertrophic and atrophic scars.
The severity and extent of hidradenitis suppurativa is recorded at assessment and when determining the impact of a treatment. The Hurley system describes three distinct clinical stages:
- Solitary or multiple, isolated abscess formation without scarring or sinus tracts
- Recurrent abscesses, single or multiple widely separated lesions, with sinus tract formation
- Diffuse or broad involvement, with multiple interconnected sinus tracts and abscesses.
Severe hidradenitis (Hurley Stage 3) has been associated with:
What is the treatment for hidradenitis suppurativa?
- Weight loss; follow an anti-inflammatory, low-sugar, low-grain, low-dairy diet (mainly plants)
- Smoking cessation: this can lead to improvement within a few months
- Loose fitting clothing
- Daily unfragranced antiperspirants
- If prone to secondary infection, wash with antiseptics or take bleach baths
- Apply hydrogen peroxide solution or medical grade honey to reduce malodour
- Apply simple dressings to draining sinuses
- Analgesics, such as paracetamol (acetaminophen), for pain control.
Medical management of hidradenitis suppurativa
Medical management of hidradenitis suppurativa is difficult. Treatment is required long term. Effective options are listed below.
- Topical clindamycin, with benzoyl peroxide to reduce bacterial resistance
- Short course of oral antibiotics for acute staphylococcal abscesses, eg flucloxacillin
- Prolonged courses (minimum 3 months) of tetracycline, metronidazole, cotrimoxazole, fluoroquinolones, ertapenem or dapsone for their anti-inflammatory action
- 6–12 week courses of the combination of clindamycin (or doxycycline) and rifampicin for severe disease.
- Long-term oral contraceptive pill; antiandrogenic progesterones drospirenone or cyproterone acetate may be more effective than standard combined pills. These are more suitable than progesterone-only pills or devices.
- Spironolactone and finasteride
- Response takes 6 months or longer.
Immunomodulatory treatments for severe disease
- Intralesional corticosteroids into nodules
- Systemic corticosteroids short-term for flares
- Methotrexate, ciclosporin, and azathioprine
- TNF-α inhibitors adalimumab and infliximab, used in higher dose than required for psoriasis, are the most successful treatments to date. Note that paradoxically, they may sometimes induce new-onset hidradenitis suppurativa
- Other biologics are under investigation, such as the IL-1β antagonist, canakinumab
Other medical treatments
- Metformin in patients with insulin resistance
- Acitretin (unsuitable for females of childbearing potential)
- Isotretinoin — effective for acne but appears unhelpful for most cases of hidradenitis
Surgical management of hidradenitis suppurativa
- Incision and drainage of acute abscesses
- Curettage and deroofing of nodules, abscesses and sinuses
- Laser ablation of nodules, abscesses and sinuses
- Wide local excision of persistent nodules
- Radical excisional surgery of entire affected area
- Nd:YAG laser hair removal