Erythema Nodosum Overview Definition: • EN is an inflammatory condition characterized by tender, red nodules, typically located on the shins. Nature: • It is a form of panniculitis, involving inflammation of the subcutaneous fat. Significance: • EN often serves as a marker for underlying systemic diseases. Common Causes of EN: • Infectious Agents: - Streptococcal infections (most common) - Mycobacterium tuberculosis - Histoplasma capsulatum - Yersinia enterocolitica - Chlamydia trachomatis - Mycoplasma pneumoniae - Coccidioides immitis - Epstein-Barr virus • Systemic Diseases: - Sarcoidosis - Inflammatory bowel disease (Crohn’s disease, ulcerative colitis) - Behçet's disease • Medications: - Sulfonamides - Oral contraceptives - Penicillins - Omeprazole - Hepatitis B vaccine • Other Factors: - Pregnancy - Malignancies (e.g., non-Hodgkin lymphoma, pancreatic cancer) - Idiopathic (no identifiable cause in 30–50% of cases) Clinical Presentation of Erythema Nodosum (EN): • EN typically presents as the sudden onset of painful, erythematous, warm nodules or plaques, most commonly located on the anterior aspects of the lower legs (shins). • The lesions are usually bilateral but may be asymmetric, and they range in size from 1 to 5 cm. Patients may also report systemic symptoms such as fever, malaise, arthralgia (especially in the ankles and knees), and fatigue. • The nodules evolve over several days, starting as bright red and becoming violaceous, then fading to a bruise-like appearance before resolving spontaneously over 2 to 8 weeks without ulceration or scarring. Diagnostic Approach: Clinical Evaluation: • Detailed patient history and physical examination. Laboratory Tests: • Complete blood count (CBC) • Erythrocyte sedimentation rate (ESR) • C-reactive protein (CRP) • Antistreptolysin O (ASO) titer • Throat culture • Tuberculin skin test • Chest radiograph (especially to assess for sarcoidosis) Histopathology: • Skin biopsy may reveal septal panniculitis without vasculitis Management Strategies: Address Underlying Cause: • Treat infections, manage systemic diseases, discontinue offending drugs. Symptomatic Treatment: • Nonsteroidal anti-inflammatory drugs (NSAIDs) for pain and inflammation. • Bed rest and leg elevation. • Compression therapy. • Potassium iodide for persistent cases. • Corticosteroids or colchicine in refractory cases. Prognosis: • EN is generally self-limiting, resolving within 3–6 weeks. • Recurrence is possible, especially if the underlying cause persists. #Erythema #Nodosum #Diagnosis #Management
