What are the causes of erythema nodosum (EN)?

Causes of erythema nodosum (EN)

  • Bacterial infections: Streptococcus, Yersinia, Salmonella, Campylobacter, Chlamydia, Mycoplasma 
  • Mycobacterial infection: TB, leprosy 
  • Viral infection: Infectious mononucleosis, hepatitis B, herpes simplex 
  • Other infection: Tinea, toxoplasma 
  • Drugs: Sulfa drugs, OCP, potassium iodine agents 
  • Malignant disease: Malignant lymphoma (Hodgkin's disease etc.), leukaemia 
  • Inflammatory bowel disease: UC, Crohn's disease 
  • Others: Sarcoidosis, Behcet's disease, reactive arthritis (Reiter's syndrome), pregnancy 
erythema nodosum


  • Shimizu's dermatology 2nd Edition; page:385 and table 18.3
  • Rapid review of clinical medicine for MRCP part 2 by Sanjay Sharma (question no: 401)
  • Dermatology made easy 1st Edition; pages:571 & 576

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