What is erythema nodosum?
Erythema nodosum is a type of skin inflammation that is located in a certain portion of the fatty layer of skin. Erythema nodosum (also called EN) results in reddish, painful, tender lumps most commonly located in the front of the legs below the knees. The tender lumps, or nodules, of erythema nodosum range in size from one to five centimeters. The nodular swelling is caused by a inflammation in the fatty layer of skin.
Erythema nodosum can be self-limited and resolve on its own in three to six weeks. Upon resolution, it may leave only a temporary bruised appearance or leave a chronic indentation in the skin where the fatty layer has been injured.
What causes erythema nodosum?
Erythema nodosum may occur as an isolated condition or in association with other conditions. Conditions that are associated with erythema nodosum include medications (sulfa-related drugs, birth control pills, and estrogens), strep throat, Cat scratch disease, fungal diseases, infectious mononucleosis, sarcoidosis, Behcet's disease, inflammatory bowel diseases (Crohn's disease and ulcerative colitis), and normal pregnancy.