Randy Jacobs, M.D. Patient Education

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Erythema Nodosum



What Is It?

Erythema nodosum is a skin condition where red lumps form on the shins, and less commonly the thighs and forearms. Erythema nodosum of unknown origin.  Three to six women are affected for each man with erythema nodosum (EN). However the sex incidence before puberty is about equal. Most cases occur between the ages of 20 and 45, with a peak from 20 to 30. EN occurs occasionally in the elderly and in children. Erythema nodosum is a disease of the skin and its underlying structures in which red, tender nodules are found over the bones below the knees.  Other parts of the body may also be involved.  Fever and joint pain frequently accompany the other symptoms. Erythema nodosum is not a specific disease, but represents a reaction to some infection or substance to which an allergic sensitivity has developed.  The most common infection is considered to be due to streptococcal bacteria.  Certain medications can also be responsible for this type of skin response. In a nutshell , Erythema nodosum is a condition in which a person acquires multiple, red, tender nodules the shins, and less frequently on the face and arms. Erythema Nodosum is considered to be a type of delayed hypersensitivity reaction to a wide variety of provoking agents.



Who Gets It?

Erythema Nodosum can occur at any age but the highest incidence occurs in women between 20 and 30 years of age. Women acquire Erythema Nodosum 3 to 6 times more frequently than men. The greatest incidence is in spring and fall.


How Does It Begin and Progress?

EN may be preceded by an upper respiratory infection 7-14 days beforehand or by a longer period of feeling "below par", loss of weight and cough. Other symptoms depend on the cause of the EN.  Joint aches occur in over half of cases regardless of cause. The knee joints are almost always affected, the other large joints less commonly. Joint symptoms may persist for months afterwards but always resolve completely. The EN lesions are ushered in by fever, general aching and feeling unwell. Red lumps appear on the shins or about the knees and ankle. They vary in size between a cherry and a grapefruit and in number from 2 to 50 or more. Usually there are about a dozen large lumps on the front and sides of the legs and knees; the thighs, outer aspects of the arms, face and neck are less frequently involved. At these other sites the lesions are smaller and more superficial. The lesions are oval patches which are slightly raised above the surrounding surface, the elevation increasing gradually towards the center; they are hot and painful, bright red when they first come out, later becoming purple then fading through the color changes of a bruise. Lesions continue to erupt for about 10 days. The "bruising" color-change starts in the second week, becomes most marked in the third week, then subsides at any time from the end of the third week to the sixth week. Aching of the legs and swelling of the ankles may persist for some weeks, especially if the patient does not rest up. New crops of EN may occur over a number of weeks. Rarely, 2 or 3 large lesions merge to form a crescentric ring, which spreads for some days before fading. Conjunctivitis may occur. Classic Erythema Nodosum is characterized by a sudden appearance of multiple, red, warm, and tender nodules, approximately 1 cm to 15 cm in diameter, primarily occurring on both shins, but occasionally on the arms, face, calves and trunk. Erythema Nodosum is frequently preceded or accompanied by fever, generalized aching (malaise), fatigue, and aching joints (arthralgia). Erythema Nodosum may be preceded by an upper respiratory tract infection such as sore throat or bronchitis. Erythema Nodosum usually goes away within 3 to 6 weeks, but sometimes has a longer duration. Erythema Nodosum may leave bruise-like areas after the nodules subside, and these bruise-like areas may persist much longer. Chronic Erythema Nodosum is Erythema Nodosum which persists months to years without getting better. The person with this condition is usually healthy, and Chronic Erythema Nodosum is not associated with serious systemic disease.


What Causes It?

Erythema Nodosum is a type of delayed hypersensitivity reaction to provoking antigenic agents. EN appears to be a hypersensitivity reaction with a number of different causes.  Common causes are: Throat infections. These may be due to streptococcus, or viral in origin.  Sarcoidosis: EN is often associated with enlargement of the lymph nodes in the lungs in sarcoidosis. It may result in a dry cough or some shortness of breath.  Tuberculosis (TB): EN occurs with the primary infection with TB. Pregnancy or the oral contraceptive pill: EN may occur after the first 2 or 3 cycles on the pill. EN may occur in pregnancy, clear after delivery, then recur in subsequent pregnancies.  Other drugs which can cause EN include: sulfonamides, salicylates, bromides, iodides and gold salts.  There are many other causes of EN but these are uncommon. There are numerous provoking agents and/or conditions which can cause this condition. In USA and Northern and Western Europe, streptococcal infections and sarcoidosis are currently the two most important causes. In other parts of the world, tuberculosis, drugs, and fungal infections are more common, reflecting the prevalence of these diseases in their respective communities.


The cause of Erythema Nodosum is unknown in forty percent. Listed below are numerous associations:


I. Infections


A. Bacterial

 1. Streptococcal infections

 2. Tuberculosis

 3. Yersinia infection, Yersinia Enterocolitica

 4. Brucellocis

 5. Leptospirosis

 6. Tularemia

 7. Campylobacter jejuni colitis


B. Chlamydial

 1. Chlamydia Psittaci Pneumonia

 2. Lymphogranuloma Venerum

 3. Cat scratch disease


C. Fungal

 1. Coccidioidomycosis

 2. Histoplasmosis

 3. Dermatophytosis

 4. North American Blastomycosis


D. Protozoan



E. Viral

 1. Herpes simplex

 2. Infectious Mononucleosis

 3. Hepatitis B


II. Drugs


 1. Estrogens

 2. Oral Contraceptives

 3. Sulfonamides

 4. Aminopyrine

 5. Antimony compounds

 6. Arsphenamine

 7. Bromide

 8. Immunizations                               

 9. Iodides

10. Phenacetin

11. Salicylates

12. Vaccines

13. Minocycline


III. Malignancy


 1. Hodgkin's disease

 2. Leukemia

 3. Post irradiated Pelvic Cancer


IV. Miscellaneous


 A. Behcet's disease

 B. Ulcerative Colitis

 C. Crohn's disease

 D. Pregnancy

 E. Sarcoidosis

 F. Acne Fulminans

 G. Familial Erythema Nodosum


How Is It treated?

Bed rest is advised for severe EN.  Firm supportive bandages or stockings maybe worn.  Aspirin or other anti-inflammatory medication may be prescribed.  A course of potassium iodide is often effective in clearing it. Mild cases subside in 3 weeks, more severe ones in about 6 weeks. Cropping of new lesions may occur within this time, especially if the patient is not resting. The main and most important aspect of treatment is to define and treat the underlying disease and/or discontinue provoking medications. Complete bed rest is beneficial. Leg elevation is important if the patient is to find relief. To reduce pain and inflammation, Indomethacin, Naproxen, or newer non steroidal anti-inflammatory drug may be used. Corticosteroids can be useful in the presence of sarcoidosis. Corticosteroids  are best not used when the primary cause is not known. Potassium iodide is sometimes used, and is usually taken for 3 to 4 weeks. Usually, symptomatic relief is obtained within a few days.