Erythema nodosum (EN) is the most common type of septal panniculitis (inflammation of the subcutaneous fat) and results from a delayed hypersensitivity to various stimuli, such as bacterial and viral infections (most commonly Streptococcus and Epstein-Barr virus [EBV], respectively), medications, malignancies, inflammatory bowel disease (see Crohn disease, ulcerative colitis), fungal infections, and collagen vascular diseases. However, in 33%-50% of cases, no associations are found. A detailed list of etiologies is below.
The eruption persists for 3-6 weeks and spontaneously regresses without ulceration, scarring, or atrophy.
EN occurs in boys and girls in equal proportions before puberty (it rarely occurs before age 2); however, after puberty, females are more frequently affected, as in the adult population. Recurrences with reappearance of the precipitating factor(s) are reported.
Primary infectious panniculitis (see panniculitis) occurs through septic seeding or direct inoculation of a variety of infectious organisms. Tissue culture and polymerase chain reaction (PCR) aids in diagnosis.
Poststeroidal panniculitis is rare but exclusive to children. Occurs 1-10 days following withdrawal of systemic corticosteroids. May ulcerate and scar.
Cold panniculitis typically presents on the cheeks ("Popsicle panniculitis") but may occur on any body site exposed to cold temperatures. Lateral thigh involvement of horseback riders has been described.
Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.
Erythema nodosum is a skin disorder that produces red bumps under the skin that can be tender. They usually occur due to some underlying disease or use of a medication. The bumps of erythema nodosum can occur anywhere on the body but are most common on the shins. They look like raised bumps or bruises that change from pink to blue-brown.
Who’s At Risk
Erythema nodosum can occur in patients of any age, sex, or race. The inflammation is most common in females, particularly in the age range 18-34 (teens and young adults). In addition, erythema nodosum tends to occur in families who are exposed to the same trigger. While their cause to a particular individual may be unknown, people who receive immunity-weakening drugs (eg, chemotherapy drugs), oral contraceptives, and antibiotics are more likely to develop them. Also, infections and cancers can predispose a person to developing erythema nodosum.
Signs & Symptoms
The most common locations for erythema nodosum include:
Knees, ankles, or thighs
Face and neck
Erythema nodosum appears as one or more reddish, warm, and painful lumps (nodules), ranging in size from 1-10 cm.
The onset of erythema nodosum may be associated with fever, generalized achiness, leg swelling, or joint pain.
Individual nodules of erythema nodosum usually last from 1-2 weeks, but new lesions may continue to appear for up to 6 weeks. When an individual lesion of erythema nodosum has resolved, it may leave behind a temporary bruise, which subsequently fades to normal-appearing skin.
Although erythema nodosum may occur on its own, it is more often associated with a medication or with an underlying infection or medical condition. Therefore, it is important to see a physician in order to investigate any possible health problems. In the meantime, however, the tenderness of the skin lesions may be alleviated by the following:
Restriction of physical activity or bed rest
Elevation of the legs (if they are affected)
Cool or warm compresses
Generally, people with erythema nodosum do quite well, especially once any underlying medical conditions have been treated.
When to Seek Medical Care
Since erythema nodosum can be associated with underlying infections or health problems, a physician should be consulted within a few days of noticing the skin lesions.
After diagnosing you with erythema nodosum, your physician will attempt to identify a possible cause, such as medication, infection, or medical condition. The doctor may order diagnostic tests such as blood work, a chest X-ray, or a throat culture. If an underlying cause is identified, then the physician will treat it appropriately (for example, by discontinuing a medication, prescribing antibiotics for an infection, or treating a health problem).
Once those investigations and treatments are under way, your health care provider may try the following measures to make you more comfortable:
Restriction of physical activity or bed rest
Anti-inflammatory medications such as ibuprofen or aspirin
Steroids (either taken in pill form or injected directly into the lesions)
Bolognia, Jean L., ed. Dermatology, pp.724, 1455, 1552-1555. New York: Mosby, 2003.