Differential diagnosis and laboratory investigations
The differential diagnosis includes erythema multiforme, Hodgkin’s disease, Sweet’s syndrome, tuberculosis, sarcoidosis, and streptococcal infection.1,2
Erythema multiforme most often forms a characteristic target lesion. It can also present as an urticarial lesion or in a vesiculobullous form. While patients with a history of Hodgkin’s disease may exhibit erythema nodosum heralding an impending relapse, it is not generally a sign of primary disease.
Sweet’s syndrome (acute febrile neutrophilic dermatosis) is a reactive disorder generally considered to be a dermatologic manifestation of a systemic disease. In many cases an underlying systemic disease is discovered, such as myelodysplastic syndrome, nonlymphocytic leukemia, or inflammatory bowel disease. The mean age at presentation is about 56 years, with lesions well demarcated and more widespread than those of erythema nodosum.
Tuberculosis and streptococcal infections are 2 of the most common causes of erythema nodosum in children. In adults, erythema nodosum may result from streptococcal infection or sarcoidosis. Tuberculin skin testing, chest radiography, throat culture/rapid streptococcal antigen testing, and an antistreptolysin O titer should be included in a patient’s evaluation.