A patient with multibacillary leprosy is started on WHO MDT. Which drug in the regimen is responsible for the lepromatous reaction known as Lucio phenomenon?
- A Clofazimine; it triggers immune complex deposition by altering bacterial surface antigens
- B None of the MDT drugs; Lucio phenomenon is a host immune response independent of dapsone or clofazimine ✓
- C Dapsone; it causes complement-activating immune complexes in lepra bacilli-laden vessels
- D Rifampicin; rapid killing of bacilli causes antigen release precipitating Type 2 lepra reaction
Explanation
The Lucio phenomenon (also called necrotizing leprosy or erythema necroticans) is a severe, ulcerative cutaneous vasculitis occurring exclusively in diffuse, non-nodular lepromatous leprosy (Lucio leprosy). It is caused by immune complex-mediated necrotizing vasculitis in dermal blood vessels heavily infiltrated with lepra bacilli, and is NOT triggered by any specific MDT drug. It is distinct from Type 1 (reversal) and Type 2 (ENL) lepra reactions. Type 2 reactions (ENL) can be precipitated by rifampicin-induced rapid bacterial killing, but Lucio phenomenon is a spontaneous host immune response.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.