Etiology and therapeutic management of erythema nodosum during pregnancy: an update.

Erythema nodosum (EN) is the most common form of panniculitis. It is characterized by erythematous, raised, tender nodules that usually occur bilaterally on the extensor surfaces of the lower extremities. EN is associated with many underlying conditions including infection, sarcoidosis, malignancy, and pregnancy. Its underlying etiology, however, is unknown in up to half of cases. Pregnancy is thought to create an optimal background for EN to develop, although the exact mechanisms are unclear. Immune complexes may play a role in the pathogenesis of EN during pregnancy, or EN may be a hypersensitivity reaction to either estrogens or progesterone. EN is a self-limiting process, and non-pharmacologic means such as bed rest and elastic web bandages may be sufficient to control the symptoms. Potassium iodide, systemic and intralesional corticosteroids, non-steroidal anti-inflammatory drugs, salicylates, tumor necrosis factor-α inhibitors, hydroxychloroquine, colchicine, and dapsone are other treatment options available, but some of these drugs are contraindicated in pregnancy while others are considered safe. Before prescribing one of these treatments to a pregnant patient, the patient's obstetrician should be consulted, and a careful risk-benefit analysis should be performed.