Type 1 lepra reaction (reversal reaction) occurs in which part of the Ridley-Jopling spectrum and is immunologically mediated by:

• A TT and LL; immune complex deposition
• B LL only; complement-mediated cytolysis
• C Borderline leprosy (BT, BB, BL); sudden upgrading/downgrading of CMI ✓
• D Pure neuritic leprosy; T-cell anergy

Explanation

Type 1 reaction (reversal reaction) occurs exclusively in the borderline spectrum (BT, BB, BL) and reflects sudden shifts in cell-mediated immunity—either upgrading (toward TT, during treatment) or downgrading (toward LL, without treatment). It manifests as erythema and oedema of existing skin lesions with acute neuritis. Type 2 reaction (erythema nodosum leprosum, ENL) occurs in LL and BL and is mediated by immune complex deposition. The distinction is critical as management differs—Type 1 needs high-dose corticosteroids; Type 2 needs thalidomide or steroids.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.