From the Guidelines
The diagnostic approach for erythema nodosum in an 18-year-old should begin with a thorough history and physical examination, followed by targeted laboratory testing to identify the underlying cause, with a firm clinical diagnosis normally being made without the need for biopsy, as stated in the study by 1. The initial evaluation should include:
- Complete blood count
- Erythrocyte sedimentation rate
- C-reactive protein
- Throat culture for streptococcal infection
- Chest X-ray
- Tuberculin skin test Management primarily involves treating the underlying cause while providing symptomatic relief. For symptomatic treatment, the following options can be considered:
- NSAIDs like ibuprofen 400-600 mg three times daily or naproxen 500 mg twice daily as first-line options
- Bed rest and elevation of the affected limbs to reduce pain and swelling
- Potassium iodide solution (400-900 mg daily in three divided doses) to accelerate resolution of the lesions
- Colchicine 0.5-1.0 mg twice daily for recurrent cases, as recommended in the study by 1 For severe cases, systemic corticosteroids such as prednisone 40-60 mg daily with a gradual taper over 2-4 weeks may be considered, as well as immunomodulation with azathioprine, infliximab, or adalimumab in resistant cases or frequent relapses, as stated in the study by 1. The prognosis is generally good, with most cases resolving within 3-6 weeks, though lesions may continue to erupt for up to 6 weeks. Erythema nodosum represents a delayed hypersensitivity reaction to various antigens, resulting in inflammation of the subcutaneous fat, and the characteristic tender, erythematous nodules on the anterior shins reflect this inflammatory process, which typically resolves without scarring.
From the Research
Diagnostic Approach
- Erythema nodosum is an acute inflammatory dermatosis characterized by painful nodules, generally symmetrical and non-ulcerative, mainly located on the extensor surface of the lower legs 2.
- The diagnostic approach should include laboratory and instrumental examinations to identify any underlying trigger disease 2, 3.
- A diagnostic algorithm can be used to optimize the initial work-up, including an initial assessment of core symptoms, diagnostic work-up, differential diagnosis, and recommended therapies 3.
Management
- Erythema nodosum is a self-limited disease, and therapy is often only symptomatic 2.
- NSAIDs (e.g., acetyl salicylic acid, ibuprofen, naproxen, indomethacin) are usually sufficient to manage symptoms 2.
- Systemic steroids may be effective, but their use is not recommended unless necessary 2.
- Treatment options should focus on addressing the underlying cause of the disease, rather than just treating the symptoms 3.
Underlying Causes
- The most common identifiable causes of erythema nodosum include streptococcal infections, primary tuberculosis, sarcoidosis, Behçet disease, inflammatory bowel disease, drugs, and pregnancy 2, 3.
- Ruling out an underlying disease is imperative before diagnosing primary erythema nodosum 3.
- Note that study 4 is not relevant to erythema nodosum, as it discusses restless legs syndrome in patients with Parkinson disease.