Erythema nodosum

Erythema nodosum presents with tender, non-ulcerated, erythematous nodules located most commonly over the shins, and may sometimes be associated with arthralgia and fever.

Lesions occur as a response to a variety of conditions, including infection, chronic inflammatory disease, auto-immune disease, malignancy, and pregnancy. They are also related to the ingestion of certain medications.

Histopathology demonstrates a septal panniculitis without vasculitis. Miescher's radial granulomas are a diagnostical feature, but are not necessary for confirmation.

Treatment consists of supportive care, including bed rest and leg elevation, as well as non-steroidal anti-inflammatory drugs (NSAIDs), potassium iodide, and intralesional or oral corticosteroids. Nodules may also resolve spontaneously. Healing occurs without atrophy or scarring.

Erythema nodosum (EN) is a common cutaneous hypersensitivity reaction consisting of erythematous, tender nodules most commonly located over the shins, but also reported over the thighs, upper extremities, calves, buttocks, and face. Fever and arthralgia may sometimes be present. EN is the most common inflammatory condition of the subcutaneous fat, or panniculitis.

Lesions arise as single or clustered, tender patches, later evolving into painful nodules over the course of several days. Occasionally these nodules are associated with extravasated blood, resulting in the appearance of purpura. These ecchymotic areas fade into variably pigmented patches before resolving. As new crops of nodules may form weeks after the initial presentation, lesions at varying stages of resolution may coexist. Microscopy of these lesions demonstrates a septal panniculitis without vasculitis.[1]Bondi EE, Margolis DJ, Lazarus ZS. Panniculitis. In: Freedberg I, Eisen A, Wolff K, et al, eds. Fitzpatrick's dermatology in general medicine. 5th ed. New York, NY: McGraw-Hill; 1999: 1284-6.