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For further information, see CMDT PART 6-48: 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

  • Evaluation for underlying cause is essential

General Considerations

  • Erythema nodosum is a symptom complex of panniculitis characterized by tender, erythematous nodules that appear most commonly on the extensor surfaces of the lower legs

  • Most cases are idiopathic; however, they can be considered a skin sign of systemic disease

  • Disease may be associated with various infections

    • Streptococcosis

    • Primary coccidioidomycosis

    • Other deep fungal infections

    • Tuberculosis

    • Yersinia pseudotuberculosis and Y enterocolitica infection

    • Diverticulitis

    • Syphilis

  • May accompany sarcoidosis, Behçet disease, and inflammatory bowel disease

  • May be associated with pregnancy or with use of oral contraceptives

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)

Diagnosis

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

Imaging

  • All patients should have a chest radiograph

Treatment

Medications

  • 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

Outcome

Prognosis

  • 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 ...

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