ERYTHEMA NODOSUM

Erythema nodosum (EN) is the most common panniculitis and may develop in response to a wide variety of antigens. In this unique reaction pattern, exquisitely tender nodules develop on the shins.

Clinical

The typical patient experiences the acute onset of multiple deep-seated, red nodules on both shins. Pain is often severe. Some patients limp or can't even walk. It usually runs its course over 3-6 weeks. Lesions on the thighs or arms are less common. There is a a chronic variant also known as Vilanova disease that may present as a solitary, slowly enlarging red plaque on the lower leg.

Possible Causes

The most important first step is to determine, if possible, the cause. Any of a variety of antigen exposures may be implicated.

• Infections: Group A beta-haemolytic Streptococcus, Yersinia, Salmonella, Campylobacter, Mycobacterium tuberculosis, Epstein–Barr virus, Parvovirus B19, Cytomegalovirus, Dermatophytes, Hepatitis, Blastomycosis, Histoplasmosis, Coccidioidomycosis, Sporothrix, non-specific URI, chlamydia

• Drugs: Oral contraceptives, Macrolides, Cephalosporin, Penicillin, BRAF inhibitor therapy

• Inflammatory diseases: Behçet's disease, Sarcoidosis, Ulcerative colitis, Crohn's disease

• Others: Hodgkin's disease, pregnancy, radiation of a neoplasm.

• Idiopathic

Diagnosis and Workup

In most cases, a skin biopsy is not needed for diagnosis but may be helpful in atypical cases. A high fever, respiratory symptoms and/or an abnormal chest X-ray may signal a causative lung process, e.g. pneumonia. Workup may include:

• CBC (infection)
• u.a.
• ASO
• Pregnancy test
• Throat and urine cultures (Blood if indicated)
• PPD, CXR (for TB and sarcoidosis)
• ACE level (for sarcoidosis)
• liver enzymes
• stool culture if diarrhea is present
• Intradermal or serologic tests for deep fungi (if indicated)

Treatment

Mild cases may only require rest and NSAIDs, e.g., indomethacin. More severe cases often respond to SSKI (supersaturated potassium iodide). If the pain is severe and there is no evidence of ongoing infection, prednisone, e.g., 1 mg/kg, is very effective in controlling the outbreak within several days. Narcotic analgesics may be needed for the pain. Rarely, patients will need a wheelchair at home because of the pain. If the lesions are not very numerous, some have injected the lesions with IL Kenalog 5-10 mg/cc.

Additional Pictures

Villanova's Disease

RegionalDerm

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