EN is associated with a wide variety of conditions. Idiopathic About 30–50% of EN cases are idiopathic (of an unknown cause). Infection Infections associated with EN include: * Streptococcal infection which, in children, is by far the most common precipitant * Primary infection of tuberculosis * Mycoplasma pneumoniae * Histoplasma capsulatum * Yersinia * Lymphogranuloma venereum (LGV), caused by the bacteria Chlamydia trachomatis * Epstein-Barr virus * Coccidioides immitis (Valley fever) * Cat scratch disease Autoimmune disorders Autoimmune disorders associated with EN include: * Inflammatory bowel disease (IBD): about 15% of patients develop<unk> . * Behçet's disease * Sarcoidosis Pregnancy Pregnancy may be associated with EN. Medications Medications associated with EN include: * Sulfonamides * Penicillins * Bromides * Hepatitis B vaccination Cancer Cancers associated with EN include: * Non-Hodgkin's lymphoma (NHL) * Carcinoid tumours * Pancreatic 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<unk> . A useful mnemonic for causes is SORE SHINS (Streptococci, OCP, Rickettsia, Eponymous (Behçet), Sulfonamides, Hansen's Disease (Leprosy), IBD, NHL, Sarcoidosis.
Erythema nodosum
Streptococcal intertrigo
Erythema migrans
Keratolytic winter erythema
Acneiform eruption
Lichenoid eruption
Cutaneous larva migrans
Dermatitis repens