Erythema nodosum (EN) is a specific form of panniculitis (see 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.
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 disorders are
Other possible triggering disorders include
Up to one third of cases of EN are idiopathic.
Erythema induratum, a similar disorder, manifests with lesions on the calves and classically affects patients with TB.
Symptoms and Signs
EN is a subset of panniculitis that manifests as erythematous, 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 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 serial antistreptolysin O titers or a pharyngeal culture. ESR is often high.
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 should be used only as a last resort because they can worsen an occult infection. If an underlying disorder is identified, it should be treated.
Last full review/revision November 2013 by Wingfield E. Rehmus, MD, MPH
Content last modified November 2013