A 40-year-old man from rural India presents with progressive weakness and clawing of both hands with thickened ulnar nerves. He has no skin lesions anywhere, and slit-skin smears from standard sites are negative for AFB. Which investigation is most appropriate to confirm the diagnosis?

• A Biopsy of a thickened sensory cutaneous nerve branch ✓
• B Serological test for anti-PGL-I antibodies
• C Lepromin skin test
• D PCR of peripheral blood for M. leprae DNA

Explanation

Pure neuritic (polyneuritic) leprosy involves peripheral nerves without any cutaneous lesions, so slit-skin smears are unhelpful. Diagnosis requires biopsy of a sensory branch of an affected nerve, typically the radial cutaneous or sural nerve, showing granulomas or bacilli within endoneurium. The lepromin test indicates host immune status, not diagnosis, and is not confirmatory. Anti-PGL-I serology supports exposure but lacks specificity, and blood PCR is not a validated standard diagnostic method here.

Reference: IAS Textbook of Dermatology, 4th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.