Erythema Nodosum

Erythema Nodosum (EN) is a skin condition that is characterized by painful red, rounded lumps that appear on the shins and around the ankles, and less commonly in the thighs and forearms. It can occur at any age, in both sexes, and anyone.

These lumps tend to heal to leave a bruise-like appearance. EN is more common among females and is more frequently observed between the ages of 20 and 30 years.

In most patients, no cause or trigger can be identified. In some patients, a trigger can be identified. EN may sometimes be a sign of an underlying condition that needs to be identified.

The most typical causes of EN are: 

• Throat infection caused by bacteria called Streptococci
• Medication: drugs that are known triggers for EN include the contraceptive pills and some antibiotics
• Sarcoidosis: This is a rare inflammatory disease that can affect any organ in the body, but most commonly involves the lungs, lymph glands, and skin. Sarcoidosis is one of the more common triggers for EN in adults
• Inflammatory bowel disease: patients with both ulcerative colitis and Crohn’s disease may infrequently develop EN.
• Pregnancy: Pregnancy can occasionally trigger EN.

Patients with EN may feel generally unwell with a temperature shortly before or at the same time as the lumps start to appear. There may also be aching and swelling of the joints, mainly knees, ankles, and wrists.

Aching of the legs and swelling of the ankles may last for several weeks after the lumps have appeared.

EN starts as poorly defined red, painful lumps. They feel like a firm, smooth, raised projections, 2 to 6 cm in diameter on the skin, and are often very tender.

They most typically appear on the shins and around the ankles.

As the lump begins to fade, it looks more like a bruise, turning blue and then yellowish in white skin. The lumps usually clear over a period of 3–6 weeks without scarring.

The diagnosis is usually made by the doctor recognizing the rounded lumps on the skin on the specific sites. Occasionally it is necessary for a skin biopsy.

Additional investigations, usually blood tests and a chest x-ray, may be required to determine the underlying cause of EN.

Most patients with EN make a full recovery within a few weeks or months. However, in some patients, new lumps of EN may occur over several weeks,  with the condition persisting and following a long time course lasting for six months and occasionally longer.

Your doctor will look for known triggers for EN. If an infectious cause is identified, then antibiotic treatment may be given.

If a particular medication is suspected as the trigger, it may be stopped. For most people with EN, the rounded lumps tend to heal spontaneously.

Some patients may need treatment to relieve symptoms, such as bed-rest, leg elevation, and anti-inflammatory painkillers (non-steroidal anti-inflammatory agents).

For more prolonged EN, several more potent treatments may be used, such as steroid tablets.

There is not a great deal you can do to influence the course of EN other than elevating the legs when resting and avoiding too much time standing, walking, and running.