Aetiology

A wide range of antigenic stimuli are implicated:

Common causes include:

• idiopathic - up to 55%
• sarcoidosis - 30 to 40% of cases
• infectious causes:
  • streptococcal/viral throat infections - most common
  • chlamydia - relatively common
  • tuberculosis - relatively common
  • mycoplasma
  • yersinosis - more common in non-UK European countries
  • rarely, histoplasmosis, leprosy, psittacosis, cat-scratch disease, lymphogranuloma venereum
• inflammatory causes:
  • inflammatory bowel disease:
    • Crohn's
    • ulcerative colitis
  • rarely, Behcet's disease
• drugs are a common cause:
  • sulphonamides
  • oral contraceptive pill
• malignancy:
  • lymphoma, leukaemia
  • postradiation therapy
• pregnancy
  
  

Rare cause include:

• Infections
  • Viral – herpes simplex virus, Epstein-Barr virus, hepatitis B and C viruses, HIV
  • Bacterial - Campylobacter spp., rickettsiae, Salmonella spp., psittacosis
  • Parasitic - amoebiasis, giardiasis
• malignancy:
  • lymphoma, leukaemia
  • postradiation therapy
• often no cause is found (1)

Reference:

• (1) Schwarts RA, Nervi SJ. Erythema Nodosum: A Sign of Systemic Disease. AFP 2007;75(5)
• (2) Sheretz EF et al.Skin reactions to systemic disease. Medicine International (1992);102:4278-81
• (3) The Practitioner (2001);345:937-41.