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Erythema nodosum (EN) is a specific form of panniculitis (see Hypersensitivity and Inflammatory Disorders: 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, inflammatory bowel disease, and TB. Diagnosis is by clinical evaluation and biopsy. Treatment depends on the cause.
Etiology
EN primarily affects people in their 20s and 30s but can occur at any age; women are more often affected. Etiology is unknown, but an immunologic reaction is suspected because EN is frequently accompanied by other disorders; the most common are
Other possible triggers include
Up to one third of cases of EN are idiopathic.
Symptoms and Signs
EN is a subset of panniculitis that manifests as erythematous, tender plaques or nodules, primarily in the pretibial region, accompanied by fever, malaise, and arthralgia.
Diagnosis
Diagnosis is usually by clinical appearance and can be confirmed by excisional biopsy of a nodule when necessary. A diagnosis of EN should prompt evaluation for causes. Evaluation might include biopsy, skin testing (PPD or anergy panel), antinuclear antibodies, CBC, chest x-ray, and antistreptolysin O titer or pharyngeal culture. ESR is often high.
Treatment
EN almost always resolves spontaneously. Treatment includes bed rest, elevation, cool compresses, and NSAIDs. K iodide 300 to 500 mg po tid can be given to decrease inflammation. Systemic corticosteroids are effective but are an intervention of last resort as they can worsen an occult infection. If an underlying disorder is identified, it should be treated.
Last full review/revision October 2009 by Wingfield E. Rehmus, MD, MPH
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