De what is it?
Erythema nodosum is an inflammation of the fat cells located under the skin, which is caused by stimulation of the immune system. This inflammation is manifested by small painful balls (nodules), easily palpable under the skin and associated with a burning sensation, most often on the legs. You often feel sick. This stimulation of the immune system may be the result of a bacterial or viral infection, rheumatic disease, autoimmune disease, cancer, pregnancy, or a reaction to a drug. However, it is often impossible to identify the cause.
What is its frequency?
Every year, 1 to 5 in 100,000 people develop erythema nodosum. The condition is 3 to 5 times more common in women than in men, and it occurs most often between the ages of 15 and 40 years. Most cases occur in winter and spring.
How to recognize it?
Erythema nodosum is characterized by the sudden appearance of red lumps that are painful and warm to the touch, usually on both legs. The nodules can multiply over a period of 3 to 6 weeks. The condition rarely affects other parts of the body. The plates are usually between 1 and 5 centimeters long, but they can also come together into one large plate. The ankles and lower legs are often swollen. After a while, the plaques turn blue and eventually disappear. The condition does not leave scars.
You may be sick and have fever, fatigue, headache, eye infections, or joint pain. In the majority of cases, the disease resolves on its own within 3 to 6 weeks and does not relapse. In some cases, however, the erythema nodosum persists longer or the disease may return after a while.
How is the diagnosis made?
The tests aim to detect an underlying condition for which specific treatment can be started. The doctor will therefore take a blood test to measure markers of inflammation in the blood and may possibly request a screening for mononucleosis. In some situations, he will also take a urine sample or a smear from the throat (strep infection) for a culture. If he suspects a sarcoidosis, the doctor will order an x-ray of the lungs.
What can you do ?
Get enough rest and sleep. The cold, but also the hot compresses, can reduce the pain.
What can your doctor do?
If he diagnoses an underlying condition, he will immediately begin appropriate treatment. You will be given anti-inflammatory drugs for the pain.
If there is no active infection or other specific cause that can be treated, your doctor may prescribe other anti-inflammatory drugs (colchicine, hydroxychloroquine, thalidomide) or cortisone therapy.
In problematic cases, a few days of potassium iodide treatment may be helpful. Before starting treatment, the doctor will check your thyroid function and rule out possible hypersensitivity to iodine.
If he suspects an underlying disease that he cannot confirm, the doctor will refer you to a specialist.
Want to know more?
- Erythema nodosum 1 (image) – DermIS – Dermatology Information System
- Erythema nodosum 2 (image) – DermIS – Dermatology Information System
- Non-steroidal anti-inflammatory drugs – CBIP – Belgian Center for Pharmacotherapeutic Information
- Colchicine – CBIP – Belgian Center for Pharmacotherapeutic Information
- Hydroxychloroquine – CBIP – Belgian Center for Pharmacotherapeutic Information
- Thalidomide – CBIP – Belgian Center for Pharmacotherapeutic Information
- Corticosteroids – CBIP – Belgian Center for Pharmacotherapeutic Information
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