Erythema Nodosum

Updated: Jun 09, 2017
  • Author: Jeanette L Hebel, MD; Chief Editor: William D James, MD  more...
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Overview

Background

Erythema nodosum (EN) is an acute, nodular, erythematous eruption that usually is limited to the extensor aspects of the lower legs. Chronic or recurrent erythema nodosum is rare but may occur. Erythema nodosum is presumed to be a hypersensitivity reaction and may occur in association with several systemic diseases or drug therapies, or it may be idiopathic. The inflammatory reaction occurs in the panniculus.

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Pathophysiology

Erythema nodosum probably is a delayed hypersensitivity reaction to a variety of antigens; circulating immune complexes have not been found in idiopathic or uncomplicated cases but may be demonstrated in patients with inflammatory bowel disease. [1]

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Epidemiology

Frequency

United States

Peak incidence occurs at age 18-34 years. Age and sex distributions vary according to etiology and geographic location. [2]

International

Rates of erythema nodosum vary according to country. In England, the rate is 2.4 cases per 10,000 per year.

Sex

Women are affected more often than men, with a male-to-female ratio of 1:4.

Age

Erythema nodosum may occur in children and in patients older than 70 years, but it is more common in young adults aged 18-34 years. Age distribution varies with geographic location and etiology.

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Prognosis

In patients with erythema nodosum, the prognosis is excellent. In most patients, erythema nodosum resolves without any adverse reactions.

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Patient Education

Instruct patients that the restriction of physical activities may help shorten the course of erythema nodosum.

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