Causes
In about 30-50% of cases, the cause of EN is unknown. EN may be associated with a wide variety of diseases, including infections (e.g., hepatitis C, tuberculosis, streptococcal, Mycoplasma pneumoniae, Yersinia, and Epstein-Barr virus), Coccidioides immitis, sarcoidosis, autoimmune disorders (e.g., inflammatory bowel disease or Behçet's disease), pregnancy, medications (sulfonamides, oral contraceptives, bromides), vaccinations, and cancer. EN may also be due to excessive antibody production in lepromatous leprosy leading to deposition of immune complexes. There is an association with the HLA-B27 histocompatibility antigen, which is present in 65% of patients with erythema nodosum.
Read more about this topic: Erythema Nodosum