Erythema Nodosum

Basics

Description

  • Erythema nodosum (EN) is a common, acute or recurrent skin hypersensitivity reaction that results in sudden onset of multiple erythematous, symmetric, firm, nonulcerative, painful nodules or plaques that are painful to palpation
  • Normally localized to the extensor surfaces and are caused by inflammation of the septa between SC fat nodules (septal panniculitis)
  • Skin lesions are initially red, become progressively ecchymotic appearing, with spontaneous regression of lesions within 3–6 wk of initial appearance
  • Nodules vary in diameter size ranging from 0.4–4 in (1–10 cm) and are round with poorly demarcated edges
  • Female predominance, 3–5x increase compared to males, ages between 25–40, peak incidence in 3rd decade
  • Major disease variants include:
    • EN migrans (usually mild unilateral disease with little or no systemic symptoms)
    • Chronic EN (lesions spread via extension, and associated systemic symptoms tend to be milder)

Etiology

  • Immune-mediated response
  • 30–50% of the time etiology is idiopathic, otherwise commonly associated with drugs or infection
  • Noninfectious causes:
    • Drugs:
      • Oral contraceptives
      • Sulfonamides
      • Penicillin’s
    • Malignancy:
      • Lymphoma/Leukemia
    • IBD (Crohn’s or ulcerating colitis)
    • Miscellaneous
    • Pregnancy
    • Whipple disease
    • Behçet disease
    • Sarcoidosis
    • Connective tissue disorders
  • Infectious causes:
    • Post vaccination for hepatitis and TB
    • Bacterial
    • Post Streptococcal infections – most common
    • TB
    • Leprosy
    • Yersinia
    • Mycoplasma
    • Tularemia
    • Cat-scratch disease
    • Leptospirosis
    • Brucellosis
    • Chlamydia
    • Viral
    • Infectious mononucleosis
    • Hep B, Hep C
    • HIV
    • HSV
    • EBV
    • Para vaccinia
    • Fungal
    • Coccidiomycosis
    • Histoplasmosis
    • Blastomycosis
    • Parasitic
    • Amebiasis
    • Giardiasis

Pediatric Considerations

Typically, EN begins 2–3 wk after onset of streptococcal pharyngitis

No sex predominance in prepuberty population

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