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. Hidradenitis suppurativa also has a significant psychological impact, and many patients suffer from impairment of body image, depression and anxiety. 

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 proinflammatory 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 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.

Signs include:

  • Open and closed comedones
  • Painful firm papules, larger nodules and pleated ridges
  • Pustules, fluctuant pseudocysts and abscesses
  • Pyogenic granulomas
  • Draining sinuses linking inflammatory lesions
  • Hypertrophic and atrophic scars.

Many patients with hidradenitis suppurativa also suffer from other skin disorders, including acne, hirsutism and psoriasis.

The severity and extent of hidradenitis suppurativa are recorded at assessment and when determining the impact of a treatment. 

Information Source: DermNet NZ: https://dermnetnz.org/topics/hidradenitis-suppurativa/