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Erythema Nodosum

Article
Bone, Muscle, & Joint
Healthy Lungs
+5
Contributed byLester Fahrner, MD+1 moreMar 12, 2022

What are the other Names for this Condition? (Also known as/Synonyms)

  • EN (Erythema Nodosum)

What is Erythema Nodosum? (Definition/Background Information)

  • Erythema Nodosum (EN) is an inflammatory disorder characterized by ‘tender-to-touch’, red nodules or bumps under the skin. It usually occurs in the legs (especially the shins) and the arms
  • There is inflammation of subcutaneous (under the skin) fat in this condition (termed panniculitis)
  • In many individuals, the reason behind Erythema Nodosum occurrence is not well understood. However, triggers such as infection may be present in some individuals. Establishing any of these triggers is an important aspect in treating EN
  • Erythema Nodosum frequently resolves by itself in about 8 weeks. Treating the symptoms using medication, such as non-steroidal anti-inflammatories (NSAIDs), is normally the treatment required in most individuals. The prognosis of the condition is good

Who gets Erythema Nodosum? (Age and Sex Distribution)

  • Erythema Nodosum occurs primarily between the ages of 20-45 years, with a peak age from 20-30 years. However, it can occur at any age
  • The condition is up to 3-4 times common in adult females than adult males;  before puberty the case rates are equal
  • It can affect individuals of any ethnicity, race or region

What are the Risk Factors for Erythema Nodosum? (Predisposing Factors)

For unknown reasons, some individuals are at an increased risk of Erythema Nodosum. Nevertheless, the following factors may increase one’s risk of Erythema Nodosum:

  • Women are nearly 4 times more likely than men to be affected by EN
  • Use of medications that may include antibiotics (amoxicillin, penicillin, sulfonamides), birth-control pills, bromides, iodides, progestin, sulfones, and many other drugs
  • A host of infections may increase one’s risk, which include: Streptococcus sore throat, mycobacteria tuberculosis, cat scratch disease, chlamydia, fungal lung infections (such as coccidioidomycosis, histoplasmosis), hepatitis B, leprosy, leptospirosis, lymphogranuloma, mononucleosis (EBV), mycoplasma, psittacosis, syphilis, tuberculosis, tularemia, and yersinia
  • Pregnancy
  • Clinical conditions that include: Inflammatory bowel disease (such as Crohn’s disease and ulcerative colitis), cancers (such as leukemia and lymphoma), sarcoidosis, Bechet’s disease, rheumatic fever, etc.

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Erythema Nodosum? (Etiology)

Research scientists believe that Erythema Nodosum (EN) occurs due to hypersensitivity (abnormal sensitivity) to certain substances (antigens). However, in up to 50% of the individuals, no obvious triggers (precipitant) are identified.

In the remaining of the individuals, the following factors may play a role in the development of EN:

  • Bacterial, viral, or fungal infections that include: Streptococcus, cat scratch disease, chlamydia, fungal lung infections (coccidioidomycosis and histoplasmosis), hepatitis B, leprosy, leptospirosis, lymphogranuloma, mononucleosis, mycobacteria, mycoplasma, psittacosis, syphilis, tuberculosis, tularemia, yersinia, etc.
  • The use of medications such as antibiotics (amoxicillin, penicillin, sulfonamides), birth-control pills, bromides and iodides, progestin, sulfones, etc.
  • Specific-linked disorders, which include Bechet’s disease, Crohn’s disease, leukemia, lymphoma, rheumatic fever, sarcoidosis, and ulcerative colitis
  • Pregnancy

What are the Signs and Symptoms of Erythema Nodosum?

The signs and symptoms of Erythema Nodosum may include:

  • There may be signs and symptoms of an associated underlying illness, even before EN skin lesions appear
  • The individual may feel unwell with symptoms such as fever, malaise, joint aches, loss of weight, or swelling of legs or joints, which usually occur weeks before the skin lesions
  • Skin lesions: Inflamed nodules are most common on the shins of both legs, but can also appear on the feet, buttocks, calves, ankles, thighs, and the arms
    • They begin as flat, firm, hot, red, and painful lumps measuring up to an inch in length on the body. After a few days, they turn dusky red or purple; and weeks later, they become flat and brownish patches
    • These symptoms usually subside after 6 weeks, but there is always a possibility of lesion recurrence

How is Erythema Nodosum Diagnosed?

The following procedures may be used to diagnose Erythema Nodosum:

  • Thorough evaluation of the individual’s medical history and a complete physical examination including of the skin and the organs involved (in case of an underlying diseases)
  • During history taking the physician may want to know the following:
    • When the symptoms began and whether they are becoming worse
    • List of prescription and over-the-counter medications currently being taken
    • Personal and family history of skin diseases, tuberculosis, underlying diseases, etc.
  • The diagnosis is mainly based on the physical appearance of the skin lesions. Consultation with a dermatologist may become necessary, if they resemble other skin conditions
  • Skin punch biopsy: A sharp instrument is used to remove a small round piece of the skin nodule. The pathologist examines the biopsy under a microscope and arrives at a definitive diagnosis after a thorough evaluation of the clinical and microscopic findings, as well as by correlating the results of special studies on the tissues (if required)
  • Throat culture in order to rule out streptococcus sore throat infection
  • Chest x-ray to detect tuberculosis and sarcoidosis
  • PPD skin test or QuantiFERON Gold test for tuberculosis
  • Colonoscopy or other gastrointestinal diagnostic tests may be performed to rule out ulcerative colitis or Crohn’s disease
  • Blood, urine, stool and other imaging tests may be done to either diagnose or rule-out other medical conditions associated with Erythema Nodosum

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Erythema Nodosum?

There are no known major complications associated with Erythema Nodosum skin lesions.

How is Erythema Nodosum Treated?

The treatment options of Erythema Nodosum may include:

  • Leg elevation and nonsteroidal anti-inflammatory drugs (NSAIDs) are used to decrease pain and swelling of the skin lesions, and the swelling of the leg
  • Salicylate medications (aspirin) are used to reduce symptoms in individuals with sudden (acute) inflammation
  • Potassium iodide oral suspension or tablets may be helpful in some individuals
  • Bed rest
  • Hot or cold compresses to reduce discomfort
  • Corticosteroids, oral or injected intramuscularly, or directly into the EN lesions may be used. Use of corticosteroids simultaneously with NSAIDs or aspirin can lead to an increased risk of gastric bleeding
  • Treatment of underlying medical conditions

How can Erythema Nodosum be Prevented?

Not all cases of Erythema Nodosum (EN) can be prevented, because it can occur without any apparent offending agent (a trigger or a disease).

  • However, certain individuals can prevent the condition by avoiding substances that trigger EN. For example, by not taking penicillin for infections, but rather choosing a different class of antibiotics, or stopping and avoiding oral estrogen based contraception
  • Treating the underlying diseases or conditions that triggers EN from occurring

What is the Prognosis of Erythema Nodosum? (Outcomes/Resolutions)

  • Although, Erythema Nodosum may cause pain and malaise, it is a self-limiting condition that usually disappears without giving rise to any complications in about 1-2 months in most individuals. In a few cases, the condition may last for several months
  • The prognosis of other underlying condition(s) may affect the overall health of the individual

Additional and Relevant Useful Information for Erythema Nodosum:

Erythema multiforme (EM) is an acute, benign skin condition with a sudden onset that usually occurs due to medications, infections, illnesses, or for unknown reasons.

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On the Article

Krish Tangella MD, MBA picture
Approved by

Krish Tangella MD, MBA

Pathology, Medical Editorial Board, DoveMed Team
Lester Fahrner, MD picture
Reviewed by

Lester Fahrner, MD

Chief Medical Officer, DoveMed Team

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