Erythema Nodosum

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

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

Imaging

• All patients should have a chest radiograph

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

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 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