Erythema nodosum is an uncommon skin condition characterized by the presence of large, red bumps accompanied by flu-like symptoms. The disorder is usually the result of the immune system's inflammatory response to bacteria, fungi, or certain medications. Erythema nodosum is an acute condition, meaning that it comes on quickly but typically disappears in less than two months. Most cases do not lead to serious health complications, but it is important to receive medical evaluation so that a doctor can correctly identify and treat the underlying cause.
Doctors believe that most instances of erythema nodosum are caused by irregular immune system responses to pathogens like bacteria. The body's immune system produces histamines that cause skin to become irritated and bumps to form. Most people who suffer from erythema nodosum are between the ages of 18 and 40, though it can potentially afflict anyone. It appears to be more prevalent among women than men, though doctors do not fully understand why that is the case. The condition is usually found on the lower legs, especially on the shins and just under the knees.
The first sign of erythema nodosum is the actual appearance of red bumps. The nodules are often tender to the touch, and they may cause pain or burning sensations. Bumps range in size, but most are less than two inches (about five centimeters) in diameter. Over the course of about two weeks, the bumps become less painful and change in color to a bluish or yellowish hue. Symptoms of fever, chills, and joint pain may also be present in the first few weeks.
A person who believes he or she has erythema nodosum should visit a primary care physician. A doctor can usually make a diagnosis based on the physical appearance and location of bumps, though he or she may decide to conduct additional diagnostic tests to look for an underlying disease. Blood tests and a skin biopsy can reveal the presence of a particular bacterium, toxin, or fungus. The doctor may also decide to conduct a chest x-ray to look for signs of a more serious inflammatory disorder, like sarcoidosis.
Treatment for erythema nodosum depends on the underlying cause. Most infections can be treated with antibacterial or antifungal oral medications, and anti-inflammatory drugs can help lessen localized pain and swelling. With treatment, patients generally recover from their flu-like symptoms within about a week of onset, and bumps turn into yellowish bruises that persist for about two months. Many doctors suggest that their patients schedule at least one follow-up appointment during their recovery to confirm the efficacy of treatment.
