Erythema nodosum

An acute, self-limited nodular septal panniculitis characterized by tender, erythematous subcutaneous nodules, typically affecting the extensor surfaces of the lower legs, representing a hypersensitivity reaction to various triggers.

Causes

• Infectious causes

  • Streptococcal tonsillitis

  • Tuberculosis

  • Viral hepatitis

  • Salmonella infection

  • Campylobacter infection

  • Other viral or bacterial infections

• Inflammatory and autoimmune disorders

  • Sarcoidosis

  • Inflammatory bowel disease

• Pregnancy

• Medications

  • Penicillin

  • Sulfonamides

  • Birth control pills

  • TNF-α inhibitors

• Malignancy-associated inflammatory response (rare)