Erythema nodosum is a type of skin inflammation that is located in a part of the fatty layer of skin. Erythema nodosum 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 a dime to a quarter. They may be inflamed off and on for a period of weeks, then shrink and become flat, leaving a bruised appearance.
Erythema nodosum can go away on its own in three to six weeks. After it's gone, it may leave only a temporary bruised appearance or a chronic indentation in the skin where the fatty layer has been injured.
Chronic erythema nodosum is a condition in which lesions pop up elsewhere, for a period of weeks to months. However, chronic erythema nodosum that may last for years is another pattern. Chronic erythema nodosum, with intermittent recurrences, can occur with or without an underlying disease present.
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, 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.
How is erythema nodosum diagnosed?
The doctor would first do a physical exam of the rash. However, a biopsy is usually required to confirm a diagnosis of erythema nodosum.
How is erythema nodosum treated?
Erythema nodosum is initially managed by identifying and treating any underlying condition, along with the skin lesions.
Treatments for erythema nodosum include anti-inflammatory drugs, and cortisone by mouth or injection. Colchicine is sometime used effectively to reduce inflammation. Treatment must be customized for the particular patient and conditions present. It is important to note that erythema nodosum, while annoying and often painful, does not threaten internal organs and the long-term outlook is generally very good.