Erythema nodosum is a specific form of panniculitis characterized by tender, red or violet, palpable, subcutaneous nodules on the shins and occasionally other locations. It often occurs with an underlying systemic disease, notably streptococcal infections, sarcoidosis, and inflammatory bowel disease. Diagnosis is by clinical evaluation and sometimes biopsy. Treatment depends on the cause.
Erythema nodosum primarily affects people in their 20s and 30s but can occur at any age; women are more often affected.
Etiology of Erythema Nodosum
Etiology of erythema nodosum is unknown, but an immunologic reaction is suspected because erythema nodosum is frequently accompanied by other disorders.
The most common accompanying disorders are (1)
Streptococcal infection (especially in children)
Other possible triggers include
Other bacterial infections (eg, Yersinia, Salmonella, mycoplasma, chlamydia, leprosy, lymphogranuloma venereum, tuberculosis)
Fungal infections (eg, kerion, coccidioidomycosis, blastomycosis, histoplasmosis)
Viral infections (eg, Epstein-Barr, hepatitis B)
Use of medications (eg, sulfonamides, iodides, bromides, oral contraceptives)
Hematologic and solid cancers
Pregnancy
Up to about 50% of cases of erythema nodosum are idiopathic (2).
Erythema induratum, a similar disorder, manifests with lesions on the calves and classically affects patients with tuberculosis.
Etiology references
1. Schwartz RA, Nervi SJ. Erythema nodosum: a sign of systemic disease. Am Fam Physician. 2007;75(5):695-700.
2. Mert A, Kumbasar H, Ozaras R, et al. Erythema nodosum: an evaluation of 100 cases. Clin Exp Rheumatol. 2007;25(4):563-570.
Symptoms and Signs of Erythema Nodosum
Erythema nodosum is a subset of panniculitis that manifests as erythematous to purple, tender nodules or plaques, primarily in the pretibial region, often preceded or accompanied by fever, malaise, and arthralgia. Lesions may be detected more easily by palpation than inspection and can evolve into bruiselike areas over weeks.
Diagnosis of Erythema Nodosum
Clinical evaluation
Incisional wedge biopsy
Diagnosis of erythema nodosum is usually by clinical appearance and can be confirmed by incisional wedge biopsy of a nodule when necessary.
A diagnosis of erythema nodosum should prompt evaluation for causes. Evaluation might include biopsy, tuberculosis skin testing (using purified protein derivative [PPD] or anergy panel), and possibly other tests (eg, antinuclear antibodies, complete blood count, chest radiograph, and serial antistreptolysin O titers or a pharyngeal culture). Erythrocyte sedimentation rate is often high.
Treatment of Erythema Nodosum
Supportive care
Anti-inflammatory medications (rarely corticosteroids)
If an underlying disorder is identified, it should be treated.
Key Points
The most common causes of erythema nodosum are streptococcal infections (particularly in children), sarcoidosis, and inflammatory bowel disease.
Diagnose erythema nodosum primarily by clinical appearance but, when necessary, incisional wedge biopsy may be performed for confirmation.
