What is erythema nodosum?
Erythema nodosum is a fairly rare skin condition with red, tender lumps on the lower legs and, less often, the thighs and forearms. It is a form of panniculitis (inflammation of the fat tissue under the skin).
What does erythema nodosum look like?
Typical are red swellings caused by inflammation deep in the skin. The spots are particularly painful to touch and pressure. The swellings, up to 15 cm in size, typically occur on the lower legs but can sometimes also occur on the thighs and arms. Joint pains and fever occur regularly.
What causes it?
Exactly how the condition arises is not known. It is known that erythema nodosum can develop in reaction to various kinds of conditions — usually infections, but medicine use and some internal diseases can also trigger it. By far the most common cause is a throat infection with the streptococcus bacterium. Causes include bacterial infections (streptococci, tuberculosis, salmonella, mycoplasma), fungal infections, viral infections, medicines, and internal diseases (ulcerative colitis, Crohn’s disease, sarcoidosis, cancers).
Who gets it and how is the diagnosis made?
Erythema nodosum is seen mainly in people between 12 and 35 years old, and women have a 4 times greater chance than men. It is a characteristic picture, so the doctor usually has little difficulty making the diagnosis; finding the underlying cause can be harder. Investigation often involves blood tests and a chest X-ray, and if there have recently been complaints of a sore throat, a throat culture can be taken to demonstrate the streptococcus.
How is it treated?
When erythema nodosum is triggered by an infection, the skin lesions will in principle disappear on their own once the infection has gone. To speed healing and combat pain, the doctor can prescribe NSAIDs (anti-inflammatories). In many cases a compression bandage can also help the lesions disappear faster, and in severe cases bed rest is advised. The complaints disappear after 3 to 6 weeks; if healing is slow or new attacks keep occurring, the search for the trigger is usually extended.
When to see a doctor
See a doctor if you develop painful red lumps on the shins, especially with fever or joint pain, so the cause can be investigated and treatment given.