How to Diagnose Hidradenitis Suppurativa
Hidradenitis suppurativa is diagnosed clinically when three criteria are met: typical lesions (painful nodules, abscesses, sinus tracts, bridged scars, or open comedones), occurrence in characteristic flexural locations (axillae, groin, perineum, inframammary/intermammary folds, buttocks), and chronicity/recurrence (at least 2 lesions in the past 6 months OR a lifetime history of >5 lesions). 1, 2
Diagnostic Criteria
The diagnosis is entirely clinical—no laboratory tests or biopsies are required or routinely recommended 1. You must confirm all three elements:
1. Typical Lesion Morphology
Look for any combination of:
- Inflamed nodules (deep-seated, painful)
- Abscesses (fluctuant, purulent)
- Open comedones (characteristically paired/"double-ended")
- Sinus tracts/tunnels (draining or non-draining)
- Bridging scars (rope-like scars connecting previous lesion sites)
- Chronic purulent or serosanguinous discharge
- Persistent malodor 1, 2
2. Anatomic Distribution
The lesions must involve one or more predilection sites:
- Axillae
- Inguinal/groin regions
- Perineum and perianal area
- Infra- or intermammary folds
- Buttocks
- Medial thighs
- Abdominal folds
- Posterior auricular region (less common) 1, 2
Critical pitfall: Lesions outside these areas should prompt reconsideration of the diagnosis.
3. Chronicity and Recurrence
Document either:
- At least 2 recurrences within 6 months, OR
- Chronic/persistent lesions for ≥3 months, OR
- Lifetime history of >5 lesions 1, 2, 3
Initial Assessment After Diagnosis
Once diagnosed, immediately document:
Disease Severity Staging
Use Hurley staging for each affected body region 1, 2:
- Stage I: Recurrent nodules/abscesses without sinus tracts or scarring
- Stage II: Single or multiple widely separated recurrent abscesses with sinus tract formation and scarring
- Stage III: Diffuse or broad involvement with multiple interconnected sinus tracts and abscesses across an entire area
Baseline Measurements
Record at the initial visit 1:
- Pain score (Visual Analogue Scale 0-10 or numeric rating scale)
- Quality of life (DLQI or Skindex)
- Inflammatory lesion count (nodules and abscesses)
- Number of flares in the past month
- Presence of draining sinuses
When Histopathology May Be Considered
Biopsy is rarely needed 1. Consider it only when:
- The diagnosis is genuinely uncertain
- You need to exclude malignancy (squamous cell carcinoma can complicate long-standing HS)
- Atypical features suggest an alternative diagnosis
Common histologic findings include follicular hyperkeratosis, follicular occlusion, follicular rupture, keratin-containing cysts, and chronic inflammation with fibrosis 1.
Screening for Comorbidities
At diagnosis, screen for associated conditions that impact mortality and quality of life 4, 1:
Mental Health (perform at initial visit)
- Depression screening
- Anxiety screening
- Suicide risk assessment
Metabolic/Cardiovascular Risk Factors
- Blood pressure
- Fasting lipids
- HbA1c or fasting glucose
- BMI and waist circumference
Associated Skin Conditions (examine for)
- Acne vulgaris/conglobata
- Pilonidal disease
- Dissecting cellulitis of the scalp
- Pyoderma gangrenosum
Systemic Inflammatory Diseases (review of systems)
- Inflammatory bowel disease symptoms (especially Crohn's disease)
- Spondyloarthritis symptoms
Other Considerations
- Smoking status (document and offer cessation)
- Polycystic ovary syndrome (in women of reproductive age)
- Sexual dysfunction 4, 1
Common Diagnostic Pitfalls
Diagnostic delay averages 7 years 5, 6, often because HS is misdiagnosed as:
- Simple furuncles or "boils"
- Folliculitis
- Infected epidermoid cysts
- Bartholin gland abscess (in women)
- Perianal abscess
Key distinguishing features of HS:
- Recurrence in the same anatomic sites
- Presence of double comedones (pathognomonic when present)
- Rope-like bridging scars between lesions
- Chronicity despite repeated antibiotic courses for presumed "infections"
Immediate Referral Indications
Refer immediately to dermatology if 1:
- Hurley Stage III disease at presentation
- Extensive disease affecting multiple body regions
- Suspected complications (fistula formation, lymphedema, suspected malignancy)
- Failure of initial management within 12 weeks
Role of Imaging
Ultrasound is emerging as a useful adjunct 5 for:
- Assessing deep-seated lesions and sinus tracts not visible on examination
- Surgical planning
- Monitoring treatment response in deep structures
However, ultrasound is not required for diagnosis—the diagnosis remains clinical.