Rheumatology
Erythema Nodosum
Erythema nodosum (airy-theme-a no-doe-some) often occurs in otherwise perfectly healthy children. Usually, erythema nodosum first appears as one or several "bruises" on the shins that just don't go away. Typically, these are one, several, or many lesions which are tender, purple-to-red in color, and range in size from a half inch to 1 and 1/2 inches in diameter. They are often raised, may have quite definite margins or borders, and can be darker in the center.
E. nodosum, as it is sometimes called by doctors, most often occurs on the shins, but occasionally is found on the forearms, and rarely on the back, or elsewhere. It actually is occurring in the deeper (subcutaneous) layers of the skin. E. nodosum often erupts in groups (crops) of new rash, although sometimes a single new nodule/lump will appear. The nodules tend to persist for several days to weeks. As they heal, they may leave increased skin color (pigmentation) that can remain for many months. Almost always the color changes eventually completely disappear. Rarely, a small ulcer may appear in the center.
One cause of E. nodosum may be trauma, certainly a common occurrence on the lower legs of active children. Some parents notice that a particular fall or injury will be followed by the development of a new crop of red, swollen, tender nodules. In about two-thirds of cases, children with erythema nodosum will also have mild associated joint pains. It is very rare for these to develop into arthritis. The physical appearance of E. nodosum is sometimes of concern to children, parents, relatives or teachers. They should be reassured that the condition is benign, and in no way related to any form of abuse.
Your doctor, or rheumatologist, will test for several infections, and other illnesses, that are occasionally associated with E. nodosum. These include: streptococcal infections (such as "strep throat"), and hidden exposure to tuberculosis (usually by doing a skin test). Several forms of reactive arthritis, which are brief episodes of arthritis triggered by common virus or bacterial infections, can be associated with E. nodosum. These will be tested for if necessary.
Rarely, true forms of more chronic arthritis, such as lupus, sarcoidosis, inflammatory bowel diseases, and others, may begin with erythema nodosum. Your doctor will ask detailed questions about other signs of these illnesses, and may do additional tests, such as a TB skin test, an ANA, a rheumatoid factor, a sedimentation rate, CBC, and/or a chest X-ray. However, most often, E. nodosum is "idiopathic", meaning that a specific cause is never found.
In summary, erythema nodosum is usually a benign and self-limited condition. It requires no specific treatment, and most often goes away by itself.
Email pageLearn More
