Erythema nodosum is an inflammatory disorder that involves tender, red bumps (nodules) under the skin.
In about half of cases, the exact cause of erythema nodosum is unknown. Some cases may occur with:
The condition is more common in women than it is in men.
Erythema nodosum is most common on the shins, but it may also occur on other areas of the body (buttocks, calves, ankles, thighs, and arms).
The lesions begin as flat, firm, hot, red, painful lumps approximately an inch across. Within a few days they may become purplish, then over several weeks fade to a brownish, flat patch.
Other symptoms may include:
The red and inflamed skin symptoms may regress to a bruise-like appearance.
Your doctor can diagnose this condition by looking at your skin. Tests that may be done include:
The underlying infection, drug, or disease should be identified and treated.
Treatment may include:
Erythema nodosum is uncomfortable, but it is usually not dangerous.
Symptoms usually go away within about 6 weeks, but may return.
Call for an appointment with your health care provider if you develop symptoms of erythema nodosum.
Schwartz RA, Nervi SJ. Erythema nodosum: a sign of systemic disease. Am Fam Physician. 2007;75(5):695-700.
Updated by: Kevin Berman, MD, PhD, Atlanta Center for Dermatologic Disease, Atlanta, GA. Review provided by VeriMed Healthcare. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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