Erythema nodosum is a very rare inflammatory disorder that affects the fatty tissue underneath the skin. It usually presents as painful, somewhat raised, red or violet-coloured nodules, that appear most commonly on the shins.
The word “erythema” comes from the Greek word “erythos” which means “red.” The word “nodosum” comes from a Latin word describing something that is full of knots. Putting it together, the name of the disease makes sense. “Erythema nodosum” means red, raised bumps on the skin.
Understanding Erythema Nodosum
Painful, red nodules
The most frequent symptom of Erythema nodosum is painful, red nodules on the front of the legs (most commonly on the shins).
If you don’t have painful nodules on your shins, you probably don’t have Erythema nodosum.
The nodules arise deep in the fatty tissue below the surface of the skin, but they can cause the surface of the skin to change in colour and texture.
Sometimes the nodules can be felt on the surface of the skin as bumps or lumps. The nodules can turn into bruises over time. They eventually go away completely after a few weeks to a couple of months.
Symptoms of Infection
Often times Erythema nodosum comes on after a Strep throat infection. When Erythema nodosum is associated with an infection, other symptoms can include fever, fatigue and general malaise (feeling unwell).
Aching joints can also occur in people with Erythema nodosum. Inflammation can cause one or many joints to become tender and sometimes swollen.
Your doctor will take a complete history and perform a thorough physical examination. There is no single lab test to confirm a diagnosis of Erythema nodosum.
These are some of the other tests that can help diagnose Erythema nodosum:
- Complete blood count (CBC) with differential to look for chronic inflammation
- Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) – markers of inflammation
- Throat swab and anti-streptolysin O titre to look for streptococcus infection
- Tuberculin skin test to look for tuberculosis infection
- Chest X-ray to look for sarcoidosis or tuberculosis infection
- Colonoscopy if inflammatory bowel disease is suspected
Sometimes a biopsy is taken to aid in the diagnosis. This means a small sample of tissue is taken through a needle inserted into the affected area.
There are many potential causes of Erythema nodosum. The most common cause is infection with streptococcus (the cause of “Strep throat”). It can also be associated with other infections including tuberculosis and fungal infections.
Erythema nodosum commonly occurs in people with other inflammatory conditions such as inflammatory bowel disease (IBD), Behçet’s disease, and sarcoidosis, an inflammatory disease that causes enlargement of the lymph nodes and acute arthritis of the lower extremities.
Sometimes, Erythema nodosum occurs in women taking oral contraceptive pills, and rarely with other medications. It can also occur in women during pregnancy.
In many cases, a specific cause of Erythema nodosum is not identified.
Erythema nodosum is typically a self-limited disorder. This means it will usually go away on its own after 2 to 8 weeks. The nodules usually go away completely and do not leave any scars.
If Erythema nodosum is associated with an infection or another inflammatory disorder, it usually gets better when the other condition is treated or is under control.
Erythema nodosum can come and go in people with associated inflammatory disorders. It tends to come back during flares of inflammatory bowel disease.
People with Erythema nodosum can lead active and productive lives with the right kinds of treatment. It is important to treat associated infections or inflammatory disorders if they are present. If you do that, no other treatment may be needed. If the nodules are still painful despite controlling the underlying condition, then specific medications may be needed.
There are many medications that can be used to treat Erythema nodosum. The choice of medications will depend on your specific symptoms.
Analgesic medications such as acetaminophen (Tylenol) can be used to treat the pain associated with Erythema nodosum.
Non-Steroidal Anti-Inflammatory Drugs or NSAIDs are very effective at reducing the inflammation associated with Erythema nodosum. They can also help relieve achy joints.
When NSAIDs are not enough to control symptoms, prednisone may help. Prednisone should not be used if you have an acute infection with Streptococcus or tuberculosis.