Erythema nodosum

Painful red lumps on the shins. Not a diagnosis in itself but a signal, and finding what triggered it is the point.

What it is

Inflammation of the fat layer beneath the skin, producing tender red or purple lumps, characteristically on the shins.

**It is a reaction pattern rather than a disease**, which is the key to understanding it: the lumps are the visible sign that something else is going on, and the clinical task is finding what.

The commonest triggers are streptococcal throat infection, sarcoidosis, inflammatory bowel disease, medicines including the combined pill and some antibiotics, pregnancy, and tuberculosis. In a substantial proportion no cause is found.

The combination of erythema nodosum, swollen chest lymph nodes and joint pain is Löfgren's syndrome, an acute form of sarcoidosis with a good outlook.

The lumps themselves are self-limiting. They evolve like bruises, changing from red through purple to yellow-green over weeks, and settle within six to eight weeks without scarring or ulceration. Lesions that ulcerate or scar are not erythema nodosum and need reassessment.

Treatment is rest, elevation, compression and anti-inflammatory medication, plus treating the underlying cause where one is found.

Investigation typically includes a throat swab, chest X-ray, blood tests and a careful history of medicines and bowel symptoms.

Signs you might notice

Tender, warm, red or purple raised lumps, typically 1 to 5 centimetres across.

Almost always on the shins, sometimes on the thighs and forearms.

Painful to touch and to walk on.

Changing colour like a bruise as they resolve.

Fever, aching joints and tiredness alongside.

Ankle swelling.

Not erythema nodosum, and needing reassessment: lumps that ulcerate, discharge or scar; lesions elsewhere without shin involvement; or a single lump.

Investigation needed: ask about a recent sore throat, bowel symptoms, cough and breathlessness, new medicines including the pill, pregnancy, and travel or TB contact.

Urgent: breathlessness, coughing blood, weight loss, or persistent fever.

How it can affect day-to-day life

Walking is genuinely painful for a few weeks, and this is often under-estimated. Rest with the legs elevated, compression stockings and adequate analgesia make a real difference, and time off work is frequently justified.

Anti-inflammatory tablets help, and should be avoided where inflammatory bowel disease is the suspected cause because they can worsen it.

The investigation is often the more important part, and people sometimes get treated for the rash without the search for the cause being completed. Asking what has been excluded is reasonable.

The chest X-ray is the single highest-yield test, because sarcoidosis and tuberculosis both show there.

Where the combined pill is the trigger, stopping it resolves it, and alternative contraception needs arranging rather than just stopping.

Recurrence happens, particularly where an underlying condition such as inflammatory bowel disease is active, and a recurrence is worth reporting as a marker of that.

Supporting someone well

Understand it as a signal. Ask what the cause is being investigated as.

Ask for a chest X-ray, throat swab and blood tests.

Mention recent sore throat, bowel symptoms, new medicines including the pill, pregnancy and any TB contact.

Rest with the legs elevated, and use compression stockings.

Use anti-inflammatory medication unless inflammatory bowel disease is suspected.

Expect six to eight weeks, and no scarring.

Get lesions that ulcerate or scar reassessed; that is not this.

Report a recurrence, particularly with bowel or chest symptoms.

Get breathlessness, weight loss or persistent fever assessed urgently.

Where to get help

A GP practice for diagnosis and investigation.

Dermatology, respiratory or gastroenterology depending on the suspected cause.

Urgent assessment for breathlessness, coughing blood or persistent fever.

SarcoidosisUK and Crohn's and Colitis UK where those causes are found.