- An inflammatory disease of the deep dermis and subcutaneous fat (panniculitis) characterized by tender red nodules, predominantly in the pretibial region but occasionally involving the arms or other areas).
- In adults, streptococcal infections, tuberculosis and sarcoidosis are the most common causes;
- in children, erythema nodosum is most commonly caused by URIs, especially from streptococci.
- Less common causes include, coccidioidomycosis, histoplasmosis, primary TB, psittacosis, lymphogranuloma venereum, and ulcerative colitis.
- The condition can also be a reaction to drugs (sulfonamides, iodides, bromides, oral contraceptives).
- Resembling bruises, the nodules gradually change from pink to bluish to brown. Fever and arthralgia are frequent, and hilar adenopathy is less frequent. The condition is most common in young adults and may recur for months or years. A prolonged search for systemic infection or a causative drug may be required. In many cases, no cause can be determined. An elevated ESR is the most common laboratory finding.
- Bed rest helps to relieve painful nodules.
- If an underlying streptococcal infection is suspected, antibiotic therapy is beneficial.
Aspirin may help relieve severe symptoms when there is no evidence of underlying infection or drug etiology, although lesions often recur. When there are few lesions, intralesional triamcinolone acetonide (2.5 to 5 mg/mL) may provide symptomatic relief. Potassium iodide 300 to 600 mg/day for up to 8 wk has been advocated as an alternative treatment. Systemic corticosteroids, often the only means of controlling the lesions, may mask an underlying systemic disease.