Erythema nodosum

Clinic

• EN is an inflammatory condition characterized by inflammation of the fat cells under the skin, resulting in tender red nodules or lumps that are usually seen on both shins
• EN is presented by raised, tender red nodules usually appearing on the shins due to inflammation of the underlying subcutaneous tissue, characterized by septal panniculitis.
• EN often starts with flu-like symptoms (Fever / Cough), Malaise/ Weight loss and Aching / Stiffness / Swelling in the joints and .
• Nodules (rounded lumps) below the skin surface, usually on the Shins/ Arms / Thighs / Torso.
• Each nodule typically disappears after around two weeks, though new ones may continue to form for up to six or eight weeks.
• Nodules usually appears red and is hot and tender.
• Arthritus

Less common variants include:

• Ulcerating forms, seen in Crohn's disease
• Erythema contusiforme, when a subcutaneous hemorrhage occurs, causing the lesion to look like a contusion.
• Erythema nodosum migrans / Subacute nodular migratory panniculitis: A rare form of chronic EN characterized by asymmetrical nodules that are mildly tender and migrate over time.

Causes

• About 30–50% of ENs are idiopathic

• Infectious causes
  • Streptococcal infection
  • Primary infection of MTB
  • Mycoplasma pneumoniae
  • Histoplasma capsulatum
  • Yersinia
  • Lymphogranuloma venereum (LGV), caused by the bacteria Chlamydia trachomatis
  • EBV
  • Coccidioides immitis (Valley fever)
  • Cat scratch disease

• Autoimmune causes
  • IBD (15%)
  • Behçet's disease
  • Sarcoidosis

It is he most common type of skin manifestation of crohn's disease

Miasms

• EBV
• HBV
• HCV
• HIV
• MTB