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For further information, see CMDT PART 6-47: ERYTHEMA NODOSUM

Key Features

Essentials of Diagnosis

  • Painful red nodules without ulceration on anterior aspects of legs

  • Slow regression over several weeks to resemble contusions

  • Women are predominantly affected by a ratio of 10:1 over men

  • Some cases associated with infection, inflammatory bowel disease, or drug sensitivity

General Considerations

  • Most cases are idiopathic; however, erythema nodosum can be a sign of systemic disease

  • The disease may be associated with various infectious and noninfectious conditions

    • Infection: streptococcal, coccidioidomycosis, other fungal (eg, histoplasmosis, blastomycosis), tuberculosis, diverticulitis, syphilis, Yersinia enterocolitica

    • Other: sarcoidosis, medications (eg, oral contraceptives), inflammatory bowel disease, pregnancy, Behçet disease

Clinical Findings

Symptoms and Signs

  • The subcutaneous swellings are exquisitely tender and may be preceded by fever, malaise, and arthralgia

  • They are most often located on the anterior surfaces of the legs below the knees but may occur on the arms, trunk, and face

  • The lesions, 1–10 cm in diameter, are at first pink to red; with regression, all the various hues seen in a contusion can be observed

Differential Diagnosis

  • Erythema induratum (associated with tuberculosis)

  • Nodular vasculitis

  • Erythema multiforme

  • Lupus panniculitis

  • Poststeroid panniculitis

  • Contusions or bruises

  • Sweet syndrome (acute febrile neutrophilic dermatosis)

  • Subcutaneous fat necrosis (associated with pancreatitis)


History and Physical Examination

  • History should include inquiring about medication exposures, prior upper respiratory infection, and diarrheal illness

  • Significant physical examination findings include symptoms of any deep fungal infection endemic to the area

Laboratory Tests

  • Partial protein derivative (PPD)

  • Blood interferon gamma release assay (such as QuantiFERON) (see Pulmonary Tuberculosis)

  • Two consecutive ASO/DNAse B titers at 2- to 4-week intervals


  • All patients should have a chest radiograph



  • See Table 6–2

  • First identify and treat the underlying cause

  • Primary therapy is with nonsteroidal anti-inflammatory drugs

  • Saturated solution of potassium iodide, 5–15 drops three times daily, may result in prompt involution in many cases

  • Systemic therapy directed against the lesions themselves may include use of corticosteroids unless contraindicated by associated infection



  • It usually lasts about 6 weeks and may recur

  • If no underlying cause is found, a significant underlying illness (usually sarcoidosis) will develop in only a small percentage of patients over the next year

When to Refer

  • If there is a question about the diagnosis, if recommended therapy is ineffective, or specialized treatment is necessary



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