Erythema nodosum usually is caused by a reaction to a drug, an infection (bacterial, fungal, or viral), or another disorder such as inflammatory bowel disease.
Typical symptoms include fever, joint pain, and characteristic painful red bumps and bruises on the person's shins.
The diagnosis is based on symptoms and may be supported by results of tests that suggest a possible cause, a chest x-ray, blood tests, and a biopsy.
People stop taking suspected drugs, underlying conditions or infections are treated, and pain is relieved by bed rest, nonsteroidal anti-inflammatory drugs, and sometimes a corticosteroid.
(See also Introduction to Hypersensitivity Reactions and Inflammatory Skin Disorders Introduction to Hypersensitivity and Inflammatory Skin Disorders The immune system plays a vital role in maintaining the health of all the tissues of the body. The immune system reacts to invaders, such as microorganisms, foreign substances, or cancer cells... read more .)
People in their 20s and 30s, particularly women, are most prone to the disorder.
Quite often, erythema nodosum is a symptom of some other disease or is a reaction to a drug, but the cause is unknown in up to one third of affected people.
The most common triggers include
Other possible triggers include other bacterial infections (such as tuberculosis Tuberculosis (TB) Tuberculosis is a chronic contagious infection caused by the airborne bacteria Mycobacterium tuberculosis. It usually affects the lungs. Tuberculosis is spread mainly when people breathe air... read more ), viral infections (such as hepatitis B Hepatitis B, Acute Acute hepatitis B is inflammation of the liver that is caused by the hepatitis B virus and that lasts from a few weeks up to 6 months. Hepatitis B is spread through contact with blood or other... read more ), various drugs (such as sulfa antibiotics and oral contraceptives), pregnancy, Behçet disease Behçet Disease Behçet disease is chronic blood vessel inflammation (vasculitis) that can cause painful mouth and genital sores, skin lesions, and eye problems. The joints, nervous system, and digestive tract... read more , and several types of cancer.
The painful nodules are usually the telltale sign for the doctor.
Sometimes a nodule is removed and analyzed with a microscope (biopsy) to confirm the diagnosis.
Other testing is done to look for possible causes and can include a chest x-ray, blood tests, and skin testing for tuberculosis.
Erythema nodosum almost always resolves on its own, and the nodules may go away in 3 to 6 weeks without treatment. Bed rest, cool compresses, elevation of the legs, and nonsteroidal anti-inflammatory drugs may help relieve the pain caused by the nodules. Potassium iodide tablets may be given to decrease inflammation.
Corticosteroids taken by mouth are effective but are given only as a last resort because they can worsen an underlying infection even if one has not been identified.
Drugs that might be causing erythema nodosum are stopped, and any underlying infections or disorders are treated. If the disorder is caused by a streptococcal infection, a person may have to take antibiotics, such as penicillin, or a cephalosporin.