A leprosy patient is classified as multibacillary by the Ridley-Jopling scale (borderline lepromatous, BI = 4+). After 1 year of WHO-MDT (rifampicin + clofazimine + dapsone), he develops erythema nodosum leprosum (ENL). Which of the following best describes the immunology and management of ENL?
- A ENL is a Type 2 lepra reaction mediated by immune complex (Type III hypersensitivity) deposition with complement activation; managed with thalidomide (first line in non-pregnant adults) or prednisolone; MDT is continued ✓
- B ENL is a Type 1 lepra reaction driven by CMI reversal; treat with prednisolone alone and continue MDT
- C ENL indicates dapsone resistance; switch to rifampicin + ofloxacin + minocycline (ROM) regimen and stop clofazimine
- D ENL is triggered by dying bacilli releasing endotoxin; treat with anti-TNF biologics and suspend MDT until reaction subsides
Explanation
ENL (Type 2 lepra reaction) occurs predominantly in lepromatous (LL) and borderline lepromatous (BL) leprosy with high antigen load. It is mediated by immune complex (antigen–antibody) deposition in tissues with complement activation (Type III hypersensitivity), causing tender erythematous nodules, fever, neuritis, iritis, and orchitis. TNF-alpha also plays a role. Thalidomide is the most effective drug for ENL in non-pregnant adults; prednisolone is used when thalidomide is contraindicated. MDT must NOT be stopped. Type 1 (reversal) reaction is CMI-driven and treated with prednisolone only. ENL does not indicate dapsone resistance.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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