In leprosy, a borderline tuberculoid (BT) patient upgrades to tuberculoid (TT) type during reaction. This Type 1 (reversal) reaction is characterized by:
- A Immune-complex deposition, neutrophil infiltration, and systemic fever — an Arthus phenomenon
- B IgE-mediated mast cell degranulation causing urticaria and angioedema
- C Sudden increase in cell-mediated immunity causing inflammation and edema in existing lesions, with risk of acute nerve damage ✓
- D Erythema nodosum leprosum from deposition of IgG-bacterial antigen complexes
Correct answer: C. Sudden increase in cell-mediated immunity causing inflammation and edema in existing lesions, with risk of acute nerve damage
Explanation
Type 1 (reversal) reaction in borderline leprosy represents an abrupt shift toward enhanced Th1/cell-mediated immunity. Existing skin lesions become acutely inflamed, swollen, and tender; peripheral nerves become acutely edematous with risk of permanent motor and sensory deficit if not promptly treated with corticosteroids. It can occur during MDT and is most common in BT and BB types. Erythema nodosum leprosum (ENL, Type 2 reaction) is an immune-complex (Type III) phenomenon occurring in BL/LL.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.