Erythema nodosum in association with newly diagnosed hairy cell leukemia and group C streptococcus infection.

Erythema nodosum is an inflammatory reaction of the skin characterized by tender erythematous patches or nodules, usually located on the lower extremities. This report illustrates an association of erythema nodosum with a rare malignancy and an uncommon infectious agent in humans. There are many diseases associated with erythema nodosum; we propose that hairy cell leukemia and group C streptococcus be considered among this list.