Erythema nodosum is an inflammatory disorder. It involves tender, red bumps (nodules) under the skin.
In about half of cases, the exact cause of erythema nodosum is unknown. The remaining cases are associated with an infection or other systemic disorder.
Some of the more common infections associated with the disorder are:
Erythema nodosum may occur with sensitivity to certain medicines, including:
Sometimes, erythema nodosum may occur during pregnancy.
Other disorders linked to this condition include leukemia, lymphoma, sarcoidosis, rheumatic fever, Bechet disease, and ulcerative colitis.
The condition is more common in women than it is in men.
Erythema nodosum is most common on the front of the shins. It may also occur on other areas of the body such as buttocks, calves, ankles, thighs, and arms.
The lesions begin as flat, firm, hot, red, painful lumps that are about 1 inch (2.5 centimeters) across. Within a few days, they may become purplish in color. Over several weeks, the lumps fade to a brownish, flat patch.
Other symptoms may include:
Your health care provider 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 not dangerous in most cases.
Symptoms most often go away within about 6 weeks, but may return.
Call your provider if you develop symptoms of erythema nodosum.
Reviewed By: David L. Swanson, MD, Vice Chair of Medical Dermatology, Associate Professor of Dermatology, Mayo Medical School, Scottsdale, AZ. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.