How do you differentiate between hidradenitis suppurativa and an enlarged lymph node?

Differentiating Hidradenitis Suppurativa from Enlarged Lymph Nodes

Hidradenitis suppurativa (HS) and enlarged lymph nodes can be differentiated through their characteristic clinical presentations, locations, and progression patterns, with HS typically showing recurrent inflammatory nodules in intertriginous areas while lymph nodes maintain an oval shape with distinct anatomical distribution.

Key Differentiating Features

Location

• Hidradenitis Suppurativa:

  • Occurs primarily in apocrine gland-bearing areas: axillae, groin, perineum, anogenital region, buttocks, inframammary folds, and abdominal folds 1, 2
  • Lesions are typically in the dermis and subcutaneous tissue

• Lymph Nodes:

  • Found in specific anatomical locations: cervical, axillary, inguinal regions
  • Located in the deep subcutaneous tissue 3
  • Follow predictable anatomical drainage patterns

Clinical Appearance

• Hidradenitis Suppurativa:

  • Double-headed comedones (pathognomonic) 4
  • Painful inflammatory nodules, abscesses, sinus tracts
  • Draining tunnels with foul-smelling discharge
  • Scarring and fibrosis in chronic disease 1
  • Multiple lesions at different stages of evolution

• Lymph Nodes:

  • Oval shape with hypoechoic rim and hyperechoic center on ultrasound 3
  • Usually mobile and discrete
  • May be tender but typically not as painful as HS lesions
  • No sinus tract formation or characteristic discharge

Disease Course

• Hidradenitis Suppurativa:

  • Chronic, recurrent, and progressive 4
  • Waxing and waning of individual lesions (spontaneous regression within weeks to months) 1
  • Development of sinus tracts and scarring over time
  • Hurley staging can be applied (I, II, III) based on sinus tract formation and scarring 1

• Lymph Nodes:

  • Usually temporary enlargement in response to infection
  • May persist if underlying cause continues
  • No characteristic scarring or sinus tract formation
  • Significant enlargement only in late-stage HS (Hurley stage III) 3

Diagnostic Approach

History

1. Duration and pattern:

   • HS: Chronic, recurrent lesions with periods of flare and remission
   • Lymph nodes: Often acute enlargement related to infection

2. Associated symptoms:

   • HS: Pain, discharge, malodor, restricted mobility
   • Lymph nodes: May have systemic symptoms like fever, night sweats, weight loss if pathological 1

3. Risk factors for HS:

   • Family history (up to 42% report family history) 1
   • Obesity, smoking, female gender 2
   • Post-pubertal onset 1

Physical Examination

1. Inspect for characteristic HS lesions:

   • Double-headed comedones
   • Multiple lesions at different stages
   • Sinus tracts and scarring
   • Typical distribution in intertriginous areas

2. Lymph node assessment:

   • Discrete, mobile nodules following lymphatic chains
   • Uniform consistency
   • No sinus tract formation or scarring

Diagnostic Testing

1. Ultrasound:

   • Can differentiate HS lesions from lymph nodes
   • Lymph nodes show normal oval shape with hypoechoic rim and hyperechoic center 3
   • HS shows dermal thickening, fluid collections, and tunnel formation

2. Biopsy (rarely needed):

   • HS: Follicular hyperkeratosis, hyperplasia, occlusion with associated spongiform infundibulofolliculitis 1
   • Lymph nodes: Normal lymphoid tissue or specific pathology

Important Distinctions

1. Pain characteristics:

   • HS: Severe, debilitating pain is characteristic
   • Lymph nodes: Usually mild tenderness unless significantly inflamed

2. Discharge:

   • HS: Thick, mucopurulent, foul-smelling discharge 4
   • Lymph nodes: No characteristic discharge unless suppurative

3. Multiplicity:

   • HS: Multiple lesions at different stages of evolution
   • Lymph nodes: Usually multiple nodes in a specific region

4. Response to antibiotics:

   • HS: Limited response to short courses of antibiotics 1
   • Infectious lymphadenopathy: Often responds to appropriate antibiotics

Common Pitfalls

1. Misdiagnosing HS as recurrent skin infections

   • HS is primarily an inflammatory disease, not infectious 5
   • Cultures often show mixed flora or skin commensals 1

2. Failing to recognize HS early

   • Average delay in diagnosis is significant
   • Early recognition prevents disease progression 2

3. Overlooking lymph node enlargement in late-stage HS

   • Significant lymph node enlargement occurs in Hurley stage III disease 3
   • May reflect secondary infection rather than primary involvement

4. Not considering other differential diagnoses

   • Crohn's disease with cutaneous manifestations
   • Pilonidal sinus
   • Lymphogranuloma venereum
   • Tuberculosis with scrofuloderma

By carefully assessing the clinical presentation, location, and progression pattern, clinicians can effectively differentiate between hidradenitis suppurativa and enlarged lymph nodes, leading to appropriate management strategies and improved patient outcomes.