Erythema nodosum leprosum (ENL) is a severe immune-mediated complication of lepromatous and borderline lepromatous leprosy. It is classified as a Type 2 leprosy reaction, resulting in painful skin nodules, systemic inflammation, and multi-organ involvement. ENL significantly contributes to morbidity in affected individuals, often necessitating prolonged treatment and medical intervention.
Pathophysiology of Erythema Nodosum Leprosum
ENL is primarily driven by an immune complex-mediated inflammatory response. Excessive levels of pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β), contribute to the systemic symptoms observed in ENL.
Mechanism of ENL
Clinical Features
Cutaneous Manifestations
- Painful, erythematous nodules on the face, trunk, and extremities
- Ulceration and necrosis in severe cases
- Recurring nature with episodic flare-ups
Systemic Symptoms
- Fever (low-grade to high-grade)
- Malaise and fatigue
- Polyarthritis and joint pain
- Lymphadenopathy
- Nephritis and glomerulonephritis (in severe cases)
Risk Factors
- High bacterial load (multibacillary leprosy)
- Immune dysregulation
- Genetic predisposition
- Intercurrent infections or stress
- Treatment with multi-drug therapy (MDT)
Diagnosis
ENL is diagnosed based on clinical presentation, histopathology, and laboratory findings. Key diagnostic markers include:
- Biopsy: Dense neutrophilic infiltration with immune complex deposition
- Blood Tests:
- Elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR)
- Increased TNF-α and IL-6 levels
Treatment Approaches
First-Line Therapy
- Corticosteroids: Prednisolone (0.5–1 mg/kg/day) for inflammation control
- Thalidomide: Highly effective but teratogenic (contraindicated in pregnancy)
- Clofazimine: Anti-inflammatory effects, used in moderate cases
Adjunctive Treatments
- Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) for pain relief
- Immunosuppressants (e.g., methotrexate, cyclosporine) in refractory cases
- Anti-TNF agents in severe or recurrent cases
Prognosis and Long-Term Management
While ENL is chronic and relapsing, early diagnosis and treatment significantly reduce morbidity. Long-term management includes:
- Regular follow-ups to monitor relapses
- Pain management strategies
- Psychosocial support for patients facing stigma
