Causes of Erythema Nodosum
Common
- Idiopathic (up to 55 percent)
- Infections: streptococcal pharyngitis (28 to 48 percent), Yersinia spp. (in Europe), mycoplasma, chlamydia, histoplasmosis, coccidioidomycosis, mycobacteria
- Sarcoidosis (11 to 25 percent) with bilateral hilar adenopathy
- Drugs (3 to 10 percent): antibiotics (e.g., sulfonamides, amoxicillin), oral contraceptives
- Pregnancy (2 to 5 percent)
- Enteropathies (1 to 4 percent): regional enteritis, ulcerative colitis
Rare (less than 1 percent)
Infections
- Viral: herpes simplex virus, Epstein-Barr virus, hepatitis B and C viruses, human immunodeficiency virus
- Bacterial: Campylobacter spp., rickettsiae, Salmonella spp., psittacosis, Bartonella spp., syphilis
- Parasitic: amoebiasis, giardiasis
Miscellaneous: lymphoma, other malignancies
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