Erythema Nodosum
Basics
Description
- A delayed-type IV hypersensitivity reaction to various antigens, or an autoimmune reaction presenting as a panniculitis (1) that affects subcutaneous fat
- The clinical pattern of multiple, bilateral, erythematous, tender nodules in a typically anterior pretibial distribution that undergo a characteristic pattern of color changes, similar to that seen in bruises. Unlike erythema induratum, the lesions of erythema nodosum (EN) do not typically ulcerate.
- Occurs most commonly on the shins; less commonly on the thighs, forearms, trunk, head, or neck
- Often associated with nonspecific prodrome including fever, weight loss, and arthralgia
- Often idiopathic but may be associated with a number of clinical entities
- Usually remits spontaneously in weeks to months without scarring, atrophy, or ulceration
- Uncommon to have recurrences after the initial presentation
- Divided into acute (more common) and chronic (rare)
Pregnancy Considerations
May have repeat outbreaks during pregnancy
Pediatric Considerations
A rare pediatric variant has lesions only on palms or soles, often unilateral; typically has a shorter duration in children than in adults
Epidemiology
Frequently observed in women aged 18 to 34 years (2)
Incidence
- 1 to 5/100,000/year
- Predominant age: 20 to 30 years
- Predominant sex: female > male (6:1) in adults
Prevalence
- Varies geographically depending on the prevalence of disorders associated with EN
- Reported 1 to 5/100,000
Etiology and Pathophysiology
- Idiopathic: up to 55%
- Infectious: 44%; streptococcal pharyngitis (most common), mycobacteria, mycoplasma, chlamydia, mycoplasma, coccidioidomycosis, rarely can be caused by Campylobacter spp., rickettsiae, Salmonella spp., psittacosis, syphilis
- Sarcoidosis: 11–25%
- Drugs: 3–10%; sulfonamides amoxicillin, oral contraceptives, bromides, azathioprine, vemurafenib
- Pregnancy: 2–5%
- Enteropathies: 1–4%; ulcerative colitis, Crohn disease, Behçet disease, celiac disease, diverticulitis
- Rare causes: <1% (3)
- Fungal: dermatophytes, coccidioidomycosis, histoplasmosis, blastomycosis, Kerion of Celso
- Viral/chlamydial: infectious mononucleosis; lymphogranuloma venereum; paravaccinia; HIV; hepatitis B, C
- Malignancies: lymphoma/leukemia, sarcoma, myelodysplastic syndrome
- Sweet syndrome
- Sorafenib, pembrolizumab, dupilumab
- COVID-19 virus, SARS-CoV-2 vaccine (4)
Risk Factors
See “Etiology and Pathophysiology.”
Commonly Associated Conditions
See “Etiology and Pathophysiology.”
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Citation
Domino, Frank J., et al., editors. "Erythema Nodosum." 5-Minute Clinical Consult, 33rd ed., Wolters Kluwer, 2025. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688642/all/Erythema_Nodosum.
Erythema Nodosum. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2025. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688642/all/Erythema_Nodosum. Accessed December 3, 2024.
Erythema Nodosum. (2025). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (33rd ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688642/all/Erythema_Nodosum
Erythema Nodosum [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2025. [cited 2024 December 03]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688642/all/Erythema_Nodosum.
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