ESSENTIALS OF DIAGNOSIS
Painful nodules without ulceration on anterior aspects of legs.
Slow regression over several weeks to resemble contusions.
Women are predominantly affected by a ratio of 10:1 compared to men.
Some cases associated with infection, inflammatory bowel disease, or medication exposure.
Erythema nodosum is a symptom complex characterized by tender, erythematous nodules that appear most commonly on the extensor surfaces of the lower legs. It usually lasts about 6 weeks and may recur. Most cases are idiopathic in nature. However, erythema nodosum can be considered a skin sign of systemic disease. Evaluation and management includes making the diagnosis, treating the symptoms, and searching for an underlying cause. The disease may be associated with various infections—streptococcosis, primary coccidioidomycosis, other deep fungal infections, tuberculosis, Yersinia pseudotuberculosis and Y enterocolitica infection, diverticulitis, or syphilis. It may accompany sarcoidosis, Behçet disease, and inflammatory bowel disease. Erythema nodosum may be associated with pregnancy or with use of oral contraceptives.
The subcutaneous swellings are exquisitely tender and may be preceded by fever, malaise, and arthralgia. They are most often located on the anterior surfaces of the legs below the knees but may occur on the arms, trunk, and face (eFigure 6–87). The lesions, 1–10 cm in diameter, are at first pink to red; with regression, all the various hues seen in a contusion can be observed (Figure 6–36) but, as a rule, the lesions do not ulcerate.
Erythema nodosum. Nodules on the legs are usually very tender. (Reproduced, with permission, from Orkin M, Maibach HI, Dahl MV [editors]. Dermatology. Originally published by Appleton & Lange. Copyright © 1991 by The McGraw-Hill Companies, Inc.)
Erythema nodosum. (Used, with permission, from TG Berger, MD, Dept Dermatology, UCSF.)
Evaluation of patients presenting with acute erythema nodosum should include a careful history (including medication exposures) and physical examination. Significant findings include a history of prior upper respiratory infection or diarrheal illness or symptoms of any deep fungal infection endemic to the area. All patients should get a chest radiograph, a purified protein derivative or blood interferon gamma release assay (such as QuantiFERON) (see Pulmonary Tuberculosis in chapter 9-13), and two consecutive ASO/DNAse B titers at 2- to 4-week intervals. Coccidioidomycosis should be looked for in patients from endemic areas. If no underlying cause is found, only a small percentage of patients will go on to develop a significant underlying illness (usually sarcoidosis) over the next year.
Unlike other forms of panniculitis, a defining feature of erythema nodosum is ...