Symptoms may disappear in a few weeks or persist for 2 years, but they always resolve without destructive joint changes. The rheumatoid factor is negative. Similar lesions may appear on the extensor aspects of the forearms, thighs, and trunk. The border is poorly defined, with size varying from 2 to 6 cm. Lesions are oval, and Pathogenesis and etiology.
EN is a reaction pattern elicited by many different diseases.
The most common cause today is streptococcal infection and tuberculosis in children and streptococcal infection and sarcoidosis in adults. Leprosy is another possible inciting factor. Clinically, erythema nodosum leprosum resembles EN, but the histologic picture is that of leukocytoclastic vasculitis. EN should be considered as a warning signal of impending relapse in a patient with a history of Hodgkin's disease. Dental treatment and the possible presence of infectious dental foci should be considered in the differential diagnosis.