Erythema nodosum is the most frequent clinicopathological variant of panniculitis. The disorder usually exhibits a sudden onset of symmetrical, erythematous, tender, rounded or oval nodules and raised plaques predominantly located on the extensors of lower extremities. The peak incidence is closed to the 20–30 years of age and the sex ratio favours females. At the initial stages, the nodules show a bright red colour evolving toward red or purplish lesions and finally exhibit a yellow or greenish appearance. The clinical picture is always that of a nonspecific systemic illness with mild-grade fever, arthralgias with sometimes arthritis and fatigue, while associated illness, in case of any, may prevail the presentation. Histopathologically, erythema nodosum is the stereotypical example of a mostly septal panniculitis with no vasculitis. The septa of subcutaneous fat are always thickened and variously infiltrated by inflammatory cells that extend to the periseptal areas of the fat lobules. EN is associated with a wide variety of diseases; infections (bacterial, viral or fungal), inflammatory and autoimmune disorders (sarcoidosis, rheumatologic diseases, inflammatory bowel diseases, etc.), malignancies and medications are the most commonly associated conditions.
Usually, EN regresses spontaneously within a few weeks. The course is benign and the prognosis is excellent. Bed rest and restriction of physical activities is encouraged during the active phase. Nonsteroidal anti-inflammatory drugs or colchicine may be helpful to enhance recovery. Systemic corticosteroids are very rarely indicated in EN, and because of the benign nature of EN, they may sometimes be used locally in cases of severe arthritis. However, an underlying infection or other disease that may be masked after corticosteroid treatment should be ruled out before any administration.
KeywordsBenign Nature Erythema Nodosum Behcet Disease Hypersensitivity Mechanism Underlying Infection