Hidradenitis Suppurativa (Axillary)

Understanding Hidradenitis Suppurativa (Axillary): A Comprehensive Guide

Hidradenitis Suppurativa (HS), particularly when affecting the axillary (underarm) regions, is a chronic, inflammatory skin condition that can significantly impact a patient's quality of life. Characterized by recurrent abscesses, sinus tracts, and scarring, HS in the armpits is a common and often debilitating manifestation of this complex disease. This guide, presented from the perspective of a specialist in cosmetic and reconstructive surgery, aims to provide a thorough understanding of axillary HS, covering its underlying mechanisms, clinical presentation, diagnostic approaches, and the spectrum of therapeutic interventions available.

Executive Overview: What is Axillary Hidradenitis Suppurativa?

Hidradenitis Suppurativa (HS) is a chronic, relapsing, inflammatory disorder of the pilosebaceous unit, primarily affecting apocrine gland-bearing areas of the skin. The axillae (armpits), groin, and perianal regions are the most commonly involved sites. Axillary HS specifically refers to the manifestation of this condition within the underarm areas.

The disease typically begins with the formation of deep-seated, tender nodules and abscesses that can rupture, leading to the development of interconnected tunnels (sinus tracts) beneath the skin. Over time, these lesions can cause significant pain, disfigurement, and functional impairment due to scarring and inflammation. The chronic nature of HS means that patients often experience periods of flare-ups interspersed with periods of remission, though complete resolution is rare without intervention.

From a cosmetic and reconstructive surgery standpoint, axillary HS presents unique challenges. Beyond the medical management of inflammation and infection, the resulting scarring, contractures, and chronic wounds necessitate specialized surgical techniques to restore both form and function to the affected areas. Early diagnosis and appropriate management are crucial to minimize disease progression and its long-term sequelae.

Detailed Pathophysiology, Etiology, and Risk Factors

The precise etiology of Hidradenitis Suppurativa remains incompletely understood, but current research points to a multifactorial pathogenesis involving follicular occlusion, immune system dysregulation, and genetic predisposition.

Pathophysiology: The Unfolding Process

The prevailing theory suggests that HS originates from the occlusion of the hair follicle infundibulum. This blockage leads to a buildup of keratin and sebum, creating a microenvironment conducive to bacterial proliferation and inflammation.

1. Follicular Occlusion: The initial event is believed to be a defect in follicular keratinization, causing the hair follicle to become plugged. This blockage traps sebum, keratin, and resident bacteria.
2. Inflammatory Cascade: The trapped material triggers an inflammatory response within and around the follicle. Neutrophils, macrophages, and other immune cells infiltrate the area, releasing pro-inflammatory cytokines (e.g., TNF-α, IL-1, IL-6).
3. Follicular Rupture and Abscess Formation: The intense inflammation and pressure can lead to the rupture of the follicular epithelium, spilling inflammatory material into the surrounding dermis and subcutaneous tissue. This results in the formation of painful, tender nodules and abscesses.
4. Sinus Tract Development: Chronic inflammation and repeated episodes of abscess formation and healing lead to the development of sinus tracts. These are subcutaneous tunnels lined with inflammatory tissue that connect multiple abscesses and may open to the skin surface.
5. Fibrosis and Scarring: The persistent inflammatory process stimulates fibroblasts to produce collagen, leading to significant fibrosis and scarring. This scarring can result in disfigurement, contractures, and limitations in movement, particularly in the axillae.
6. Secondary Bacterial Infection: While not the primary cause, secondary bacterial colonization (often with Staphylococcus aureus) is common and contributes to the perpetuation of inflammation and the formation of purulent exudate.

Etiology: The Underlying Causes

The exact trigger for the initial follicular occlusion is unknown, but several factors are implicated:

• Genetic Predisposition: A family history of HS is a significant risk factor. Mutations in genes like NCSTN, PSEN1, PSEN2, and GATA3 have been linked to familial forms of HS, suggesting a role for aberrant Notch signaling and other developmental pathways.
• Hormonal Influences: HS typically emerges after puberty, and its prevalence is higher in women, suggesting a role for androgens and other sex hormones. Hormonal fluctuations, such as those during the menstrual cycle, can trigger or exacerbate symptoms.
• Immune System Dysregulation: An overactive immune response, particularly involving the innate immune system and inflammatory cytokines like TNF-α, plays a central role in the chronic inflammation seen in HS.
• Microbiome Alterations: Changes in the skin microbiome may contribute to the inflammatory process.

Risk Factors

Several factors increase an individual's risk of developing or experiencing more severe HS:

• Obesity: Increased body mass index (BMI) is strongly associated with HS. Friction, moisture, and altered skin flora in intertriginous areas (like the axillae) in obese individuals may contribute.
• Smoking: Tobacco use is a well-established risk factor and is often associated with more severe disease. The mechanisms are not fully elucidated but may involve altered immune function and vascular effects.
• Family History: As mentioned, a genetic predisposition is a significant risk factor.
• Female Sex: HS is more common in women, with a reported female-to-male ratio of approximately 3:1.
• Certain Medical Conditions: HS can be associated with other inflammatory conditions like acne conglobata, dissecting cellulitis of the scalp, and inflammatory bowel disease (e.g., Crohn's disease).

Signs, Symptoms, and Clinical Presentation

The clinical presentation of axillary HS is variable but follows a characteristic pattern of progression.

Typical Symptoms

Patients typically present with:

• Pain: Deep, throbbing, or burning pain in the affected axillary region. Pain can be severe, especially during flares.
• Tenderness: The lesions are often exquisitely tender to touch.
• Recurrent Nodules and Abscesses: These are the hallmark lesions. They typically appear as firm, red, painful lumps that can grow rapidly and fluctuate. They may resemble boils or carbuncles.
• Pustules: Small, pus-filled bumps may be present.
• Sinus Tracts: Over time, the abscesses may drain and leave behind persistent, open or closed tunnels beneath the skin. These are often characterized by intermittent drainage of pus or serosanguinous fluid.
• Scarring: Erythematous, hypertrophic, or atrophic scars are common, particularly in long-standing disease. Bridging scars and contractures can develop, restricting arm movement.
• Malodor: Chronic drainage from sinus tracts can lead to a characteristic unpleasant odor.

Clinical Stages (Hurley Classification)

The Hurley staging system is commonly used to classify the severity of HS:

• Stage I: Simple abscess formation without sinus tracts or scarring. Lesions are isolated and do not recur frequently.
• Stage II: Recurrent abscesses with formation of sinus tracts and scarring. There is typically separation of lesions by healthy skin.
• Stage III: Diffuse involvement with multiple interconnected sinus tracts and abscesses across the entire axillary region, often with extensive scarring and bridging.

Table 1: Clinical Manifestations by Hurley Stage

Standard Diagnostic Evaluation & Workup

The diagnosis of axillary HS is primarily clinical, based on a thorough patient history and physical examination. However, in certain cases, further investigations may be warranted to rule out other conditions or to assess disease severity.

Diagnostic Criteria

The International Hidradenitis Suppurativa (IHS) Foundation has proposed diagnostic criteria:

1. Typical Lesions: Characteristic lesions (nodules, abscesses, sinus tracts, scarring) in typical locations (axillae, groin, perianal).
2. Chronicity: Lesions present for at least 6 months.
3. Recurrence: Lesions repeatedly appear and disappear.

Exclusion Criteria: The diagnosis should exclude other conditions with similar presentations, such as:

• Acne vulgaris
• Folliculitis
• Carbuncles/furuncles
• Pilonidal cysts
• Epidermoid cysts
• Crohn's disease (perianal disease)
• Tuberculosis

Workup and Investigations

• Clinical History: A detailed history focusing on the onset, duration, frequency of flares, previous treatments, family history, smoking status, and associated medical conditions is essential.
• Physical Examination: A comprehensive examination of the axillary regions, looking for the characteristic lesions (nodules, abscesses, sinus tracts, scarring) and assessing the extent of involvement and Hurley stage. Examination of other typical HS sites (groin, buttocks, inframammary folds) is also important.
• Laboratory Assays:
  • Complete Blood Count (CBC): May show elevated white blood cell count and inflammatory markers (ESR, CRP) during acute flares, but is often normal in remission.
  • Cultures: Swabs from draining lesions can be sent for bacterial culture and sensitivity testing to identify secondary pathogens and guide antibiotic therapy. However, HS is not primarily a bacterial infection.
• Imaging:
  • Ultrasound (High-Resolution Musculoskeletal Ultrasound): Can be useful in delineating the extent of subcutaneous tracts, abscesses, and inflammation, especially in complex or refractory cases. It can help differentiate between inflammatory lesions and other subcutaneous masses.
  • Magnetic Resonance Imaging (MRI): Considered the gold standard for imaging in HS. MRI can provide detailed anatomical information about the depth and extent of sinus tracts, abscesses, and fibrosis, which is invaluable for surgical planning.
• Biopsy:
  • Skin Biopsy: While not routinely necessary for diagnosis, a biopsy can be considered if the diagnosis is uncertain or to rule out other conditions. Histopathology typically shows chronic inflammation, follicular rupture, abscess formation, and foreign body giant cell reaction.

Therapeutic Interventions: A Multimodal Approach

The management of axillary HS requires a comprehensive, multidisciplinary approach, often involving dermatologists, surgeons, and other specialists. Treatment goals include reducing inflammation, controlling pain, preventing new lesions, healing existing lesions, minimizing scarring, and improving quality of life.

Pharmacotherapy

Pharmacological treatments aim to modulate the inflammatory process and control bacterial superinfections.

• Antibiotics:
  • Topical: Clindamycin and erythromycin may be used for mild inflammatory lesions.
  • Oral: Tetracyclines (doxycycline, minocycline) are often the first-line oral antibiotics due to their anti-inflammatory properties. Other options include clindamycin, rifampicin, and metronidazole, often used in combination. Long-term antibiotic use is common but carries risks.
• Anti-inflammatory Agents:
  • Topical Corticosteroids: Can provide temporary relief for localized inflammation.
  • Systemic Corticosteroids: Short courses may be used for severe flares but are not suitable for long-term management due to side effects.
• Biologics (TNF Inhibitors):
  • Adalimumab (Humira): The first biologic agent approved for moderate to severe HS. It targets Tumor Necrosis Factor-alpha (TNF-α), a key inflammatory cytokine. Other biologics are being investigated.
• Other Systemic Medications:
  • Acitretin: An oral retinoid that can be effective in some cases, particularly those with associated acneiform lesions.
  • Dapsone: An anti-inflammatory and antibiotic agent.
  • Immunomodulators: Azathioprine, ciclosporin, and methotrexate have been used in refractory cases.
  • Hormonal Therapy: Oral contraceptives or spironolactone may be considered in women with suspected hormonal triggers.

Surgical Interventions

Surgery plays a critical role in managing moderate to severe HS, particularly when medical therapy fails or when there is significant scarring and sinus tract formation. Cosmetic and reconstructive surgery expertise is vital for optimizing outcomes.

• Incision and Drainage (I&D): For acute, fluctuant abscesses, I&D can provide immediate pain relief and reduce inflammation. However, it does not address the underlying disease and lesions often recur.
• Incisionless Surgery: Techniques like the "seton" placement (a thread or drain passed through sinus tracts) can promote drainage and allow for healing of tracts over time.
• Excision of Lesions/Sinus Tracts:
  • Local Excision: Removal of individual nodules or small areas of sinus tracts.
  • Wide Excision: This is the definitive surgical approach for extensive HS. It involves the complete removal of all affected skin and subcutaneous tissue, including sinus tracts, abscesses, and scarred areas.
    • Techniques for Reconstruction: Following wide excision, reconstruction is crucial to restore the contour and function of the axilla. Options include:
      • Primary Closure: For smaller defects, direct closure of the wound edges.
      • Skin Grafts: Split-thickness or full-thickness skin grafts can cover larger defects.
      • Local Flaps: Using adjacent skin and subcutaneous tissue to cover the defect.
      • Free Flaps: In complex cases with significant tissue loss, free tissue transfer from another part of the body may be necessary.
  • Laser Therapy: CO2 laser ablation can be used for superficial sinus tracts and to ablate inflammatory lesions.
• Deroofing: A technique where the roof of the sinus tract is surgically opened and the lining is debrided, allowing the tract to heal by secondary intention.

Lifestyle Modifications and Adjunctive Therapies

• Weight Management: For obese patients, weight loss can significantly improve symptoms and reduce disease severity.
• Smoking Cessation: Essential for all smokers with HS.
• Hygiene: Gentle cleansing of the affected areas with non-perfumed, antibacterial soaps can help reduce bacterial load. Avoid harsh scrubbing.
• Clothing: Wearing loose-fitting, breathable cotton clothing can minimize friction and moisture in the axillae.
• Diet: While no specific diet is proven to treat HS, some patients report improvement with anti-inflammatory diets or by avoiding triggers like dairy or gluten. This should be discussed with a healthcare provider.
• Pain Management: Over-the-counter or prescription pain relievers can help manage discomfort.

Long-Term Prognosis

The long-term prognosis for axillary Hidradenitis Suppurativa varies significantly depending on the severity of the disease, the promptness and effectiveness of treatment, and patient adherence to management strategies.

• Chronic and Relapsing Nature: HS is a chronic condition, and complete cure is rare. Most patients experience relapses and remissions throughout their lives.
• Disease Progression: Without adequate treatment, HS can progress, leading to more severe scarring, chronic pain, functional impairment, and a significantly reduced quality of life.
• Impact on Quality of Life: Beyond physical symptoms, HS can have profound psychological effects, including depression, anxiety, social isolation, and body image issues, due to pain, malodor, and disfigurement.
• Surgical Outcomes: Definitive surgical excision offers the best chance for long-term remission in localized areas of severe disease. However, recurrence can still occur in previously unaffected areas or at the margins of excised tissue. Reconstructive surgery aims to restore function and improve cosmetic appearance, but significant scarring may persist.
• Systemic Comorbidities: Patients with HS have an increased risk of certain comorbidities, including inflammatory bowel disease, metabolic syndrome, cardiovascular disease, and certain types of cancer. Regular medical monitoring is important.
• Importance of Multidisciplinary Care: Patients who receive care from a multidisciplinary team, including dermatologists and surgeons, tend to have better outcomes.

Frequently Asked Questions About Axillary Hidradenitis Suppurativa

1. Is Hidradenitis Suppurativa contagious?
No, Hidradenitis Suppurativa is not contagious. It is a chronic inflammatory skin condition, not an infection that can be transmitted from person to person.

2. Can Hidradenitis Suppurativa go away on its own?
While mild cases might experience periods of remission, HS is a chronic condition that typically does not resolve on its own. Without proper management, it often progresses and leads to more severe scarring and complications.

3. What are the main triggers for HS flares?
Common triggers include hormonal changes (menstrual cycle), stress, friction from clothing, sweating, weight fluctuations, and smoking.

4. How is Hidradenitis Suppurativa diagnosed?
Diagnosis is primarily clinical, based on the characteristic appearance of lesions (nodules, abscesses, sinus tracts, scarring) in typical locations, a history of chronicity, and recurrence. Medical imaging like MRI may be used in complex cases.

5. What is the best treatment for Hidradenitis Suppurativa?
Treatment is individualized and often involves a combination of approaches. This can include antibiotics, anti-inflammatory medications, biologics (like adalimumab), and surgical interventions such as wide excision of affected areas followed by reconstruction. Lifestyle changes like weight loss and smoking cessation are also crucial.

6. Can surgery cure Hidradenitis Suppurativa?
Surgery, particularly wide excision of affected skin and sinus tracts, offers the most definitive treatment for localized severe disease and can lead to long-term remission in those areas. However, HS is a systemic condition, and new lesions can develop elsewhere.

7. What are the long-term consequences of untreated HS?
Untreated HS can lead to severe chronic pain, extensive scarring, disfigurement, contractures limiting movement, recurrent infections, and a significant impact on physical and psychological well-being.

8. How does Hidradenitis Suppurativa affect quality of life?
The chronic pain, malodor, visible scarring, and recurrent nature of HS can lead to significant emotional distress, social isolation, depression, anxiety, and difficulties with daily activities and intimacy.

9. Is there a cure for Hidradenitis Suppurativa?
Currently, there is no known cure for Hidradenitis Suppurativa. Management focuses on controlling inflammation, healing lesions, preventing progression, and improving the patient's quality of life.

10. When should I see a cosmetic and reconstructive surgeon for Hidradenitis Suppurativa?
You should consider consulting a cosmetic and reconstructive surgeon if you have moderate to severe HS with significant scarring, chronic wounds, contractures, or if medical management has not provided adequate relief. They can assess the extent of damage and discuss surgical options for both removing diseased tissue and restoring the appearance and function of the affected area.