Erythema Nodosum
Definition And Pathophysiology
- Represents nodular erythematous hypersensitivity reaction.
- Classified morphologically as septal panniculitis.
- Inflammation strictly spares subcutaneous vasculature.
Etiologic Factors
- Idiopathic origin accounts for 30 to 50 percent of pediatric cases.
- Group A beta-hemolytic streptococcal infection represents most common childhood etiology.
- Sarcoidosis considered frequent trigger in young adults.
| Etiologic Category | Specific Associated Triggers |
|---|---|
| Bacterial Infections | Group A streptococcus, tuberculosis, Yersinia, Shigella, Escherichia coli, cat-scratch disease, leprosy, leptospirosis, tularemia, mycoplasma, Whipple disease, lymphogranuloma venereum, psittacosis, brucellosis, meningococcosis, neisserial infection, syphilis. |
| Viral Infections | Epstein-Barr virus, hepatitis B, mumps. |
| Fungal Infections | Coccidioidomycosis, histoplasmosis, blastomycosis, sporotrichosis, Trichophyton mentagrophytes. |
| Pharmacologic Agents | Cephalosporins, penicillins, macrolides, sulfonamides, bromides, estrogen-containing oral contraceptives. |
| Inflammatory And Autoimmune | Inflammatory bowel disease, ulcerative colitis, systemic lupus erythematosus, Behรงet syndrome, severe acne, celiac disease, Sweet syndrome. |
| Malignancy | Hodgkin disease, lymphoma. |
Clinical Manifestations
Cutaneous Lesions
- Manifests as multiple symmetric, oval nodules.
- Longer axis oriented parallel to extremity.
- Size varies from 1 to 6 centimeters.
- Favors lower legs, particularly pretibial area.
- Involves extensor surfaces of arms and thighs less frequently.
- Color progresses from bright or dull red to brown or purple.
- Lesions remain exquisitely painful.
- Nodules characteristically do not ulcerate.
Disease Course And Systemic Signs
- Initial lesions resolve within 1 to 2 weeks.
- New lesions continue erupting for 2 to 6 weeks.
- Recurrent episodes manifest over weeks to months.
- Systemic signs frequently precede or accompany cutaneous onset.
- Features include fever, malaise, and rheumatoid factor-negative arthritis.
- Arthralgias affect 50 to 90 percent of patients.
Histopathology
- Acute phase demonstrates distinct septal thickening.
- Inflammatory cell infiltrate composed predominantly of neutrophils.
- Chronic phase features monocyte and histiocyte predominance.
Diagnostic Evaluation
- Idiopathic form remains self-limited, requiring minimal investigation.
- Protracted or recurrent cases mandate extensive diagnostic workup.
- Recommended baseline tests include complete blood count, erythrocyte sedimentation rate, and C-reactive protein.
- Infectious screening involves throat culture and antistreptolysin O or deoxyribonuclease B titer.
- Tuberculosis screening strictly requires QuantiFERON-Tuberculosis gold assay rather than traditional skin testing.
- Chest radiograph indicated to exclude sarcoidosis or primary pulmonary infections.
Management Protocol
Conservative Therapy
- Primary intervention mandates identifying and treating underlying cause.
- Bed rest and continuous leg elevation strongly recommended.
- Nonsteroidal anti-inflammatory agents including ibuprofen, naproxen, or salicylates provide essential symptomatic relief.
Advanced Pharmacotherapy
- Indicated for persistent or severe symptoms.
- Oral supersaturated solution of potassium iodide utilized for persistent cases.
- Colchicine provides alternative therapeutic benefit.
- Intralesional corticosteroids administered for localized stubborn nodules.
- Oral corticosteroids reserved strictly for severe, persistent, or highly recurrent lesions.