Rheum

Erythema Nodosum

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Erythema Nodosum, Erythema Nodosum Migrans, Subacute Nodular Migratory Panniculitis, Chronic Erythema Nodosum

  • Epidemiology
  1. Incidence: 1-5 per 100,000
  2. Age: Peaks in 20-30 year range (up to age 50 years)
  3. Gender
    1. Adults: Women predominate by a factor of 6 fold
    2. Children: Boys and girls are equally affected
  • Pathophysiology
  1. Prototype of septal Panniculitis
  2. Affects subcutaneous fat
  3. Cutaneous Type IV delayed hypersensitivity response
  • Causes
  1. Idiopathic (up to 55% of cases)
  2. Infection
    1. Streptococcal Pharyngitis (up to 48% of EM cases)
    2. Mycoplasma
    3. Chlamydia
    4. Coccidioidomycosis
    5. Histoplasmosis
    6. Yersinia enterocolitis (in europe)
    7. MycobacteriaTuberculosis (see granulomatous disease)
  3. Granulomatous disease
    1. Tuberculosis
    2. Sarcoidosis (up to 25% of cases)
    3. Inflammatory Bowel Disease
  4. Drug Reaction (up to 10% of cases)
    1. Halides
    2. Sulfonamides
    3. Amoxicillin
    4. Gold
    5. Oral Contraceptives
  5. Pregnancy
  • Symptoms
  1. Prodrome: Acute phase response (1-3 weeks before rash)
    1. Fever
    2. Arthralgia
  2. Rash
    1. Painful "bumps" on legs
  • Signs
  1. Characteristics
    1. Erythematous Nodules
    2. Nodules are deep, warm
    3. Nodules are exquisitely tender to touch
    4. Nodules 1-10 cm (typically 2 or more cm diameter)
  2. Course
    1. Initially firm
    2. Later become fluctuant
    3. Involute over 2 week period
    4. May appear Bruised during healing
    5. Heal completely within 2 months
      1. No ulcerations, atrophy or scarring
  3. Distribution
    1. Most common on bilateral lower legs
      1. Pretibial area, anterior shins
    2. Other area involved
      1. Extensor Forearm
      2. Thighs
      3. Trunk
  4. Lesions change color over time
    1. Evolve from red to purple to brown
    2. Typically fades without scarring in a few weeks
  • Clinical variants
  1. Erythema Nodosum Migrans
    1. Persistent and minimally symptomatic lesions
  2. Subacute Nodular Migratory Panniculitis
    1. Coalescing Nodules form large Plaques on legs
  3. Chronic Erythema Nodosum
  • Labs
  1. Complete Blood Count (CBC) with Leukocytosis
  2. Sedimentation Rate (ESR) increased
  3. C-Reactive Protein increased
  4. Tuberculin Skin Test (PPD)
  5. Antistreptolysin-O titer
  6. Consider sending stool for Ova and Parasites
  7. Skin Biopsy (indicated in atypical cases)
    1. Inflammation confined to subcutaneous fat
    2. Acute lesions
      1. Septal widening
      2. Vessel wall inflammation
      3. NO Vasculitis
    3. Chronic lesions
      1. Giant cells
      2. Granulomas may be present
  • Imaging
  • Differential Diagnosis
  1. Common
    1. Alpha-1 antitrypsin deficiency
    2. Lupus Panniculitis
    3. Lymphoma (cytophagic histiocytic Panniculitis)
  2. Less common
    1. Necrobiosis Lipoidica
    2. Scleroderma
  • Management
  1. NSAIDs
  2. Bed rest with leg elevation
  3. Support stockings
  4. Treat underlying cause
  5. Potassium iodide 300-900 mg/day for one month
    1. Risk of Hyperthyroidism
  6. Consider Systemic Corticosteroids
    1. Contraindicated in Bacterial Infection or cancer
    2. Prednisone 60 mg daily and taper
  7. Intralesional injections of Corticosteroids
  • Course
  1. Most often resolves in 3-6 weeks