A case of erythema nodusum in which radicular cyst was the suspected cause of focal infection

Erythema nodusum is a non-idiopathic type of inflammation localized in the subcutaneous adipose tissue. It extends mainly to the sides of the extensor muscles of the legs and is associated with red induration, swelling, myalgia, and arthralgia. This disease also has been associated with upper tracheal infection, Behcet's disease, and Crohn's disease. However, its pathogenesis remains unknown despite many studies. We report on a man who developed erythema nodusum associated with unknown fever and arthalgia. A large radicular cyst in the right side of the maxilla was suggested to be the cause of this disease, and the association between erythema nodusum and the infectious dental focus is described in this report.