Hidradenitis suppurativa

Last revised by Mostafa Elfeky on 1 Jul 2023

Hidradenitis suppurativa, also known as acne inversa, is an inflammatory skin disease of unknown cause. It has an autosomal dominant inheritance pattern, and androgen excess has been postulated 7. The disease is associated with Crohn disease and Dowling Degos disease

Up to 4% of the general population is affected to some degree by hidradenitis suppurativa (see Hurley stages below). There is a significant female preponderance.

  • smoking appears to be a major triggering factor 7

  • obesity may aggravate the disease

Hidradenitis suppurativa is characterized by recurrent abscesses, sinus tracts and scarring in regions of predisposition. The disease affects areas bearing apocrine or sebaceous glands: groin, buttocks, inner thighs, axillae, and inframammary regions. 

Anogenital disease may tract deeply into muscle, fascia and bowel potentially leading to a "labyrinth" of disease in advanced cases 7. Notably, perianal disease specifically may mimic other common conditions such as anal fistula, pilondial disease, perianal abscess or Crohn disease 7.

Hidradenitis suppurativa is classifed clinically into three stages in the Hurley staging system 1:

  • stage 1: solitary or multiple isolated abscess formation; no scarring or sinus tracts; resembling acne vulgaris

  • stage 2: recurrent abscesses, single or multiple widely separated lesions; sinus tract formation is present; this can restrict movement and incision and drainage may be required

  • stage 3: diffuse or broad involvement across a regional area with multiple interconnected sinus tracts and abscesses; fistulisation and scarring

Based on histological features, it is considered inflammatory and originating from the hair follicle; hence, the term 'acne inversa' is favored by some experts. The exact etiology is uncertain.

The diagnosis of hidradenitis suppurativa is clinical, and imaging is non-specific.

A number of features can be identified by ultrasound. These features include both actual lesions and possible predisposing factors such as skin thickness and hair follicle morphology 5.

MRI is the test of choice to assess the extent and for complications. MRI is also useful to differentiate from Crohn disease 2, the main differential diagnosis.

STIR is considered the most useful sequence.

Focal intense FDG uptake in affected areas has been reported 4.

Management with antibiotics and other non-surgical interventions such as retinoids and corticosteroids may relieve early symptoms. Severe cases may be treated with immunosupressive agents 7.

Radical surgery (e.g. radical excision of all apocrine-bearing tissue) may be necessary for control and to prevent recurrence. Excision of affected skin however, is complicated by a recurrence rate of over 50% 7.

The condition has a significant impact on quality of life 7,11.

The differential diagnosis for hidradenitis suppurativa includes:

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