Epidemiology

• The prevalence in industrialised countries has been estimated to be 0.3-4%.^[2]
• Overall it occurs more often in women. Submammary, axillary, and inguinal involvement is more common in females, but perineal involvement is more common in men.
• Hidradenitis suppurativa is more common in white and Afro-Caribbean populations and is rare in people from Asia.

Risk factors

• Cigarette smoking^[3]
• Obesity^[3]
• Lithium therapy
• Possibly increased in patients with diabetes
• Tends to improve during pregnancy and when taking the combined contraceptive pill; tends to relapse after pregnancy and when stopping the combined contraceptive pill.

Presentation

• Usually presents between the ages of 20 and 30 years and is variable in severity and distribution.
• Predominantly occurs in the axilla, groin, perineum, perianus, buttocks, scrotum, and the submammary regions.
• Early lesions are solitary, painful and pruritic nodules and multiple sites may be affected at the same time. They may persist for weeks or months. Any subcutaneous extension appears as indurated plaques. Episodes of acute cellulitis may occur.
• The nodules develop into pustules and eventually rupture with discharge of purulent material.
• Healing occurs with dense fibrosis.
• Recurrences tend to occur in the same region, leading to chronic sinus formation, with intermittent release of serous, purulent, or bloodstained discharge. Sinus formation and rupture may occur internally into adjacent structures as well as externally.
• Regional lymphadenopathy is usually absent.

Differential diagnosis

• Acne
• Lymphogranuloma venereum
• Crohn's disease
• Furunculosis
• Actinomyces

Investigations

Patients with acute lesions may have a raised ESR, raised white blood cell count, low serum iron and serum protein abnormalities on electrophoresis.^[1]

• Full blood count: underlying anaemia associated with chronic disease
• Blood glucose: identify associated diabetes
• Microbiology swabs
• CT scans: to map the extent of disease accurately prior to surgery

Associated diseases

• Cystic acne
• Pilonidal sinus

Staging

Hidradenitis suppurativa can be divided into the following 3 clinical stages:

• Stage 1: single or multiple abscesses form, without sinus tracts.
• Stage 2: recurrent abscesses, with tract formation. Lesions may be single or multiple, localised or scattered.
• Stage 3: diffuse involvement or multiple interconnected tracts and abscesses across an entire area.

Management

• Early lesions are usually treated by medical therapy, but long-standing disease usually requires surgery.
• Radiotherapy may be effective but is controversial.^[4]

Patient advice

• Advice to patients should include good hygiene, using soaps, antiseptics and antiperspirants, warm compresses and wearing loose-fitting clothing.
• Advise weight reduction if obese, and smoking cessation.
• Beneficial activities include swimming.

Drugs

• Acute-stage:
  • Antibiotics: a short course of antibiotics for 2 weeks; therapy will be governed by swab results but erythromycin, metronidazole, minocycline, clindamycin, cephalosporins and penicillins are all effective.
  • Intralesional steroids: eg triamcinolone; cause early lesions to resolve within 12-24 hours.
• Chronic relapsing stage:
  • Long-term antibiotics: long-term erythromycin or tetracycline has been shown to reduce the relapse rate. The benefits may be lost after long-term use, and stopping therapy for a month and then restarting is recommended.
  • High-dose oral steroids to reduce the inflammation may be required.
  • Oestrogens: the combined oral contraceptive pill, particularly Dianette®, is often beneficial.
  • Retinoids: isotretinoin can be effective in chronic disease.^[5]

Surgical

Chronic sinus and tracts with recurrence are the usual indications for surgery.

• Stage 1: incision and drainage, followed by antibiotics.
• Stage 2 and some stage 3: options include laying open of tracts and electrocoagulation, or excision and primary closure.
• Stage 3: options include radical excision of all hair-bearing areas and reconstruction with a graft or a flap.^[6]

Complications

• Fistula formation into the urethra, bladder, rectum, or peritoneum may occur but is uncommon.
• Chronic infection may lead to anaemia, hypoproteinaemia, amyloidosis and renal failure.
• Chronic malaise and depression.
• Scarring may lead to lymphatic obstruction and lymphoedema.
• Generalised arthropathy may occur in long-standing disease but is uncommon.
• Squamous cell carcinoma has been reported in long-standing chronic disease.

Prognosis

• Variable but without treatment tends to be a relentless progressive disease with acute exacerbations and remissions, leading to sinus tract formation and scarring.
• Early wide excision has been shown to be followed by a low recurrence rate.^[7]