Erythema nodosum (EN) can present at any age but is most common in young, adult females. Most typical is bilateral, erythematous, subcutaneous, tender nodules on the pretibial and lateral lower extremities (usually spares the posterior calves). Rarely, the nodules can be found on the thighs, upper extremities, and face. Concomitant symptoms include lower extremity edema and arthralgias. Systemic symptoms can include fever, headache, and gastrointestinal complaints. Generally, the nodules resolve over days to weeks with flattening and a change in color to a blue-green (like a deep bruise). There is no ulceration, and the skin slowly returns to normal. Recurrence occurs in up to one-third of cases.
Erythema Nodosum, Acute. Pretibial, erythematous, and subcutaneous nodules. (Photo contributor: Gianina Best, MD.)
Erythema Nodosum, Resolving. Bruise-like appearance of the resolving phase. (Photo contributor: J. Matthew Hardin, MD.)
Multiple etiologies exist for EN, although over one-third of cases are idiopathic. Infectious causes include streptococcal, tuberculosis, Yersinia, Salmonella, Shigella, coccidioidomycosis, histoplasmosis, sporotrichosis, blastomycosis, and toxoplasmosis. EN has also been associated with pregnancy, sarcoidosis, and inflammatory bowel disease. Oral contraceptives, sulfonamides, bromides, and iodides are known to be common causative agents, among many others.
Management and Disposition
With the many etiologies of EN, it is critical to exclude and treat an infectious, systemic, or medication cause. Supportive care with elevation of the extremity, rest, and NSAIDs is helpful. Recurrences do occur and should prompt a further workup for occult infection or persistent medication. Refer patients to a dermatologist for a confirmatory biopsy, additional laboratory testing, and definitive treatment.
Erythema Nodosum. Tender subcutaneous nodules with overlying erythematous and hyperpigmented macules, indicating a new crop of lesions. (Photo contributor: J. Matthew Hardin, MD.)
The patient’s history is very helpful in determining possible etiologies. A complete medication, travel, and past medical history must be performed.
Systemic glucocorticoids can be considered, but only when the etiology is clearly known and infectious agents are excluded.
EN is considered a good prognostic sign in sarcoidosis and pregnancy-associated coccidioidomycosis.