Hidradenitis Suppurativa (Acne Inversa)

Are You Confident of the Diagnosis?

What you should be alert for in the history

Hidradenitis suppurativa (HS) is characterized by recurrent inflammatory lesions distributed bilaterally, in intertriginous areas (ie, axilla, inguinal crease, intergluteal cleft, and inframammary area). Pain and drainage of purulent material is common. The disease most commonly presents after puberty. HS often starts as a single lesion which then becomes recurrent and multifocal. Multiple short courses of antibiotics have often been tried and provide only temporary relief.

Characteristic findings on physical examination

The primary lesions include inflammatory papules and pustules, nodules, cysts and scars. Comedones often manifested by multiple openings are common. Sinus tract formation with purulent drainage is characteristic of severe disease. Extensive scarring can lead to alopecia in affected areas.

Expected results of diagnostic studies

The diagnosis is usually made clinically. Bacterial cultures are generally negative or show normal skin flora. Staphylococcus species can be found in less than half the cases. Laboratory studies are generally not necessary to diagnosis HS. When performed, anemia of chronic disease is the most common laboratory abnormality. Evaluation for B12 deficiency should be considered.

Histologic findings are variable based on the primary lesion sampled and the duration of the disease. The earliest pathologic finding is infundibular spongiosis, followed by comedone formation (Figure 1), follicular rupture and mixed inflammation (Figure 2). Severe disease could demonstrate formation of sinus tracts lined with keratinizing epithelium (Figure 3). The inflammation is usually centered in the dermis but often extends into the subcutaneous fat. Involvement of eccrine and apocrine structures can also been seen. Advanced imaging techniques, such as ultrasonography and magnetic resonance imaging (MRI) are used more to determine the extent of disease rather than the diagnosis. These techniques are often used preoperatively to guide planning the surgical approach.

Figure 1.


Figure 2.

Ruptured comedone and inflammation.

Figure 3.

Sinus tract formation.

Diagnosis confirmation

The clinical differential diagnosis includes furunculosis (usually solitary lesion not limited to intertriginous sites), inflamed epidermal inclusion cyst (usually solitary with central pore), lymphogranuloma venereum (usually unilateral inguinal lymphadenopathy with or without ulceration), scrofula (can present with linear scarring but often involves the neck), Crohn’s disease (often presents with history of diarrhea), and Nocardia infection (plaque-like scarring not limited to intertriginous area).

Who is at Risk for Developing this Disease?

Hidradenitis suppurativa has a point prevalence of 1% to 4% in the general population and is more commonly found in women (male to female ratio of 1:3). The mean age of onset is between 26 to 31. Generally, HS patients have a higher body mass index. There is no racial predeliction.

What is the Cause of the Disease?

Hidradenitis suppurativa is complex disease that has multiple etiologies. Occlusion of intertriginous areas is thought to contribute to inflammation. Obestity is common in HS patients and worsens occlusion. HS occurs almost exclusively after puberty and can flare with the menstrual cycle. A higher proportion of smokers can be found among patients with HS, suggesting a role for nicotine. Finally, HS is associated with inflammatory bowel disease and the effectiveness of anti-inflammatory medications suggest an autoimmune component.


Hidradenitis suppurativa is a part of the follicular occlusion tetrad, along with nodulocystic acne, dissecting cellulitis of the scalp, pilonidal cysts. Like, acne vulgaris, the initiating event of HS is thought to be follicular occlusion.

Histopathologically, the disease begins with infundibular spongiosis, follicular hyperkeratosis and comedone formation. Follicular rupture of these plugged follicles induces the recruitment of acute neutrophilic inflammation followed by granulomatous inflammation followed by foreign body giant cells. The mixed dermal abscess can extend deep into the subcutaneous fat and subsequently involve the sweat glands. Subsequent fibrosis and formation of sinus tracts in advanced HS is likely a result of the wound repair response to chronic inflammation, bacterial superinfection and debris.

Systemic Implications and Complications

While the clinical presentation of hidradenitis suppurativa is generally localized to the intertriginous areas, the psychological and social impact can profoundly affect the quality of life. The degree of pain can be excruciating and require specific pain management strategies. While the extent of cutaneous inflammation can be severe, there is generally no associated fever or lymphadenopathy, although rare cases of septicemia have been reported. Seronegative arthopathy has also been reported.

Rarely, hidradenitis suppurativa has been seen in association with AA amyloidosis with renal involvement. Evaluation for proteinuria and renal biopsy should be considered if there is clinical suspicion. Pyoderma gangrenosum has also been described in patients with longstanding HS. Although there is no clear correlation between disease severity, pyoderma gangrenosum can involve areas of chronic HS lesions complicating the clinical assessment.

In severe and longstanding disease, particularly in the genitofemoral region, extensive scarring can lead to damage to the lymphatic system. This can result in lymphangiectasia formation to frank lymphedema. The development of squamous cell carcinoma can also develop. Biopsy of these areas may be necessary to identify the development of carcinoma.

Treatment Options

Treatment options are summarized in Table I.

Table I.
Topical Therapy Systemic Therapy Procedural Approaches Light Therapy
Clindamycin 1% solution twice daily Clindamycin 300mg orally twice daily, plus
Rifampin 300mg orally twice daily
Intralesional steroids (triamcinolone 5-10mg/ml) CO2 Laser
Metronidazaole 1% gel twice daily Doxycycline 100mg orally twice daily “Deroofing” procedure with healing by secondary intention Nd-YAG Laser
Chlorhexidene 4% solution twice daily Minocycline 100mg orally twice daily Wide local excision Photodynamic
Hexachlorophene 3% solution twice daily Sulfamethoxazole/Trimethoprim 800/160 mg orally twice daily    
Benzoyl Peroxide 5-10% wash daily Infliximab 5mg/kg intravenously at weeks 0, 2 and 6 for induction and then every 8 weeks.    
Azelaic acid 15% gel twice daily Adalimumab 40mg intramuscular injection every other week    
  Dapsone 25-100mg orally daily    
  Spironolactone 25-100 mg orally daily    
  Isotretinoin 1mg/kg orally daily    
  Acitretin 25-50mg orally daily    

Optimal Therapeutic Approach for this Disease

The severity of hidradenitis suppurativa can be classified by the configuration and extent of inflammatory lesions and scars. This method is called the Hurley classification system. It is widely used to stratify disease severity and is useful to guide treatment at initial presentation.

-Hurley stage I (mild disease): presence of abscesses and inflammatory nodules but without scarringgure (Figure 4).

Figure 4.

Hurley stage I.

-Hurley stage II (moderate disease): presence of abssesses and inflammatory nodules with scars that are separated by intervening normal skin (Figure 5).

Figure 5.

Hurley stage II.

-Hurley stage III (severe disease): extensive interconnected scars with or without active inflamed lesions (Figure 6).

Figure 6.

Hurley stage III.

In general, the milder the disease the more likely it will respond to medical therapy. Patients often give a history using short courses of antibiotics. For mild-to-moderate disease, starting with an extended course of a systemic antibiotic is often helpful. The combination of clindamycin-rifampin for 10 weeks has been shown to be highly effective and can even induce disease remission.

The more extensive the scarring the more likely surgical intervention will be necessary. Scars and cystic lesions often represent areas of recurrent disease. These areas often have a component of epithelial sinus tract formation or foreign body reaction to keratin that require surgical removal. When these areas are small and focal, “deroofing” the lesion can offer relief and cure. Intralesional steroids are useful in aborting new abscesses while the patient is instituting therapy. Newer laser techniques with CO2 and Nd:YAG lasers also show promise in mild to moderate disease.

If there are interconnected tracts (stage III disease), surgical interventions, specifically wide local excision with a plastic surgeon experienced in treating HS should be considered. Medical intervention with potent anti inflammatory agents such as TNF-alpha inhibitors can be used as an adjunct to surgery or for patients who are poor surgical candidates.

Even with successful treatment, patients can often experience disease recurrence in nearby areas. Maintenance therapy with topical antibiotics is common to reduce frequency and severity of flares. Systemic agents such as TNF-alpha inhibitors, dapsone, oral antibiotics, and spironolactone may also be used if topical medicaments are ineffective. Intralesional steroids may be used periodically to treat specific inflammatory lesions.

Patient Management

Because hidradenitis suppurativa is a chronic disease with a recurrent waxing and waning course, it is important to note details about frequency and severity of flares by history and the number of inflammatory lesions on examination. The Hurley classification is a very useful tool to use initially but is not a dynamic assessment tool that is always useful in measuring disease improvement.

Early on, patients should be seen frequently (every 2-6 weeks) to assess and titrate therapy. Specific intervals also depend on the medications used. Unless there is an adverse reaction, it is important to have the patient on the treatment long enough (at least 2 months) to accurately assess efficacy and durability of therapy.

It is critical to understand the combinatorial approach to treatment. For severe disease, medical therapy is often more of an adjuvant therapy to definitive surgical excision. However, the patient may improve significantly on medical therapy alone and refuse the planned surgical procedure. While a minority of these patients do achieve remission on current therapies, there is often some active residual disease that should be addressed surgically or requires chronic maintenance therapy.

Lifestyle modification, including smoking cessation and weight loss, should be encouraged. Avoiding occlusive clothing can also be helpful.

Rarely, squamous cell carcinoma can develop in longstanding disease, particularly in the genitofemoral region. Unusual or unilateral lesions warrant special attention and may require biopsy for histologic analysis for possible malignancy.

Unusual Clinical Scenarios to Consider in Patient Management

The role of smoking has not been precisely defined in hidradenitis suppurativa. While no studies have clearly demonstrated that smoking cessation is an effective intervention for treating HS, it is likely smoking may contribute to HS onset and/or severity. Similarly, while obesity does correlate with HS and that body mass index (BMI) correlates with disease severity, weight loss has not definitively been shown to be an effective intervention. Nonetheless, smoking cessation and weight loss should be discussed and encouraged.

What is the Evidence?

Boer, J, Nazary , M. “Long-term results of acitretin therapy for hidradenitis suppurativa”. Br J Dermatol. vol. 164. 2011. pp. 170-5. (Retrospective study of 12 patients showing long term efficacy of acitretin for hidradenitis suppurativa. While not a comparison study with isotretinoin, this study reports that many of the responders had previously failed isotretinoin therapy and offers insights on the use of systemic acitretin with long-term follow-up.)

Gener, G, Canoui-Poitrine, F, Revuz, JE, Faye, O, Poli, F, Gabison, G. “Combination therapy with clindamycin and rifampicin for hidradenitis suppurativa: a series of 116 consecutive patients”. Dermatology. vol. 219. 2009. pp. 148-54. (This study represents the largest study of the combination of systemic clindamycin and rifampin as an effective treatment for hidradenitis suppurativa. Treatment duration of 10 weeks demonstrated a signficant improvement of median Sartorius scores. Gastrointestinal symptoms was reported in approximately 14% of patients.)

Grant, A, Gonzalez, T, Montgomery, MO, Cardenas, V, Kerdel, FA. “Infliximab therapy for patients with moderate to severe hidradenitis suppurativa: a randomized, double-blind, placebo-controlled crossover trial”. J Am Acad Dermatol. vol. 62. 2010. pp. 205-17. (This study demonstrated that approximately 25% of infliximab treated patients had greater than 50% clinical improvement after 8 weeks of therapy. Clinical improvement could be seen in some patients who continued long-term therapy.)

Hazen, PG, Hazen, BP. “Hidradenitis suppurativa: successful treatment using carbon dioxide laser excision and marsupialization”. Dermatol Surg. vol. 36. 2010. pp. 208-13. (This study describes 61 patients with chronic, refractory HS who responded to carbon dioxide laser excision and marsupialization. Most cases were performed under local anesthesia. Of 185 treated sites, only two reports of recurrence in treated locations are described.)

Kaur, MR, Lewis, HM. “Hidradenitis suppurativa treated with dapsone: A case series of five patients”. J Dermatolog Treat. vol. 17. 2006. pp. 211-3. (This small case series describes improvement of HS patients to dapsone within 4-12 weeks after instituting therapy. Dosing ranged from 50-150mg orally daily.)

Kurzen, H, Kurakawa, I, Jemec, GB, Emtestam, L, Sellhayer, K, Giamarellos-Ourboulis, EJ. “What causes hidradenitis suppurativa”. Exp Dermatol. vol. 17. 2008. pp. 455-6. (This article represents contributions from many HS experts pertaining to the current thinking and challenges.)

Lee, RA, Yoon, A, Kist, J. “Hidradenitis suppurativa: an update”. Adv Dermatol. vol. 23. 2007. pp. 289-306. (This is a review article summarizing an algorithmic approach to the medical treatment of hidradenitis suppurativa based on Hurley staging.)

van der Zee, HH, Prens, EP, Boer, J. “Deroofing: a tissue-saving surgical technique for the treatment of mild to moderate hidradenitis suppurativa lesions”. J Am Acad Dermatol. vol. 63. 2010. pp. 475-80. (This article summarizes the useful in-office technique of “deroofing” which can serve to marsupialize chronic lesions. This technique is most useful in stage I to stage II disease.)

Wolkerstein, P, Loundou, A, Barrau, K, Auquier, P, Revuz, J. “Quality of life impairment of hidradenitis suppurativa: a study of 61 cases”. J Am Acad Dermatol. vol. 56. 2007. pp. 621-3. (This study summarizes the impact of quality of life on HS patients. Multiple quality of life measurement tools are used to describe quantitatively the effect of this disease.)

Yazdanyar, S, Jemec, GB. “Hidradenitis suppurativa: a review of cause and treatment”. Curr Opin Infect Dis. vol. 24. 2011. pp. 118-23. (This review article is a concise and current summary both medical and surgical approaches to treating HS.)