Erythema Nodosum

When a person suddenly develops fever and joint pains followed by painful red bumps deep in the fat underneath the skin on the front of his legs, doctors often cut out a piece and usually diagnose erythema nodosum.

These bumps are often caused by a person's immunity trying to kill an invading germ with redness and swelling. The PPD skin test that doctors use to help diagnose tuberculosis is a similar reaction. Erythema nodosum is triggered by streptococcal infections, tuberculosis, an immune disease called sarcoidosis, deep fungus infections, intestinal infections, chlamydia, mycoplasma hepatitis, and many viruses including psittacosis that you get from birds, cat scratch fever, and even measles.

The eruption usually lasts from 3 to 6 months and may cause the ankles to swell and the joints to hurt. Then all the tender bumps usually go way by themselves without treatment. Doctors must look for a cause and then treat any infectious disease that they find. For example, they may have to treat tuberculosis, a strep throat or a fungus. Cortisone-type drugs do not shorten and may even prolong the disease. Aspirin and other nonsteroidal drugs may help relieve symptoms.

1) B Cribier, A Caille, E Heid, E Grosshans. Erythema nodosum and associated diseases. A study of 129 cases. International Journal of Dermatology 37: 9 (SEP 1998):667-672.

Checked 8/9/05

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