Erythema nodosum is the name given to extremely tender lumps on the legs and sometimes the arms caused by inflammation of the fat beneath the skin (panniculitis). The bumps look like bruises and change color in the same way, from pink to blue to brown. They are often accompanied by fever, joint pain, and redness around the eyes. They may continue to erupt for a week to 10 days, but they eventually resolve, normally within 1-2 months.

Causes

Erythema nodosum is presumed to be a type of allergic reaction either to infection or to a prescription drug. It may also be associated with inflammatory conditions. A cause is often not identified.

• Infections

• • Streptococcal infections (strep throat, tonsillitis, rheumatic fever)

• • Various viral infections (eg, infectious mononucleosis and hepatitis B)

• • Tuberculosis

• • Fungal lung infections (coccidioidomycosis, histoplasmosis)

• • Psittacosis (parrot fever)

• • Lymphogranuloma venereum (an uncommon sexually transmitted disease)

• • Leprosy (Hansen’s disease)

• Inflammatory conditions

• • Ulcerative colitis

• • Crohn’s disease

• • Sarcoidosis

• Medications

• • Sulfa drugs

• • Iodides

• • Bromides

• • Birth control pills

• Unknown causes

Risk Factors

Since erythema nodosum is relatively rare, developing any of these diseases or taking these medications will only slightly increase your risk of the disorder. Erythema nodosum is more common in young adults (20-30 years old) and females.

Symptoms

If you experience something resembling this condition, do not assume it is erythema nodosum. Sores that seem to be erythema nodosum should be evaluated by your physician.

• Very tender deep-seated lumps, like bruises, usually located on your shins

• Associated joint pain and fever

Diagnosis

Your doctor will ask about your symptoms, medications, and medical history, and perform a physical exam. You may be referred to a specialist in skin problems (dermatology) or infectious diseases.

Tests may include the following:

• Blood and urine samples

• Cultures of various bodily fluids

• Chest x-ray and other imaging tests

• PPD (skin test for tuberculosis)

• Biopsy of a lesion

Treatment

If a cause can be identified, it will be treated. For the nodules themselves, pain relief is all that is needed. They tend to resolve on their own in about six weeks without scarring. Treatment options include the following:

Pain Relief

• Bedrest and elevation of legs

• Wet compresses

• Aspirin or similar nonsteroidal anti-inflammatory

• Potassium iodide

• • Potassium iodide 300-600 milligrams per day for up to two months may alleviate the discomfort (but iodides can also cause the problem)

Steroid Treatment

This may be necessary in severe cases only.

Prevention

Some of the causes of erythema nodosum can be avoided, but the condition is rare enough that nothing but the most obvious measures are worthwhile.

RESOURCES:

American Osteopathic College of Dermatology
http://www.aocd.org/

Dermnet NZ
http://dermnetnz.org/

Dermatology
University of Maryland Medical Center
http://www.umm.edu/dermatology-info/

CANADIAN RESOURCES:

Canadian Dermatology Association
http://www.dermatology.ca/english/

Dermatologists.ca
http://www.dermatologists.ca/index.html

References:

Beers MH, Berkow R. The Merck Manual. 17th ed. Merck & Co. West Point PA; 1999.

DermAtlas. Johns Hopkins University. Available at: http://dermatlas.med.jhmi.edu/derm/result.cfm?Diagnosis=31. Accessed September 15, 2005.

Erythema nodosum. The Australasian College of Dermatologists Available at: http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Erythema_nodosum?OpenDocument. Accessed September 15, 2005.