In leprosy, the Ridley-Jopling classification grades disease on an immunological spectrum. A patient with 2 hypopigmented patches showing reduced sensation, no bacilli on slit-skin smear, and a strongly positive lepromin test is classified as:

• A Lepromatous leprosy (LL)
• B Tuberculoid leprosy (TT) ✓
• C Mid-borderline (BB)
• D Borderline lepromatous (BL)

Explanation

Tuberculoid leprosy (TT) represents the high-resistance pole: strong cell-mediated immunity with positive lepromin test, few well-defined lesions (1–5), absent or very scanty bacilli (smear-negative, BI = 0), and well-formed granulomas with Langhans giant cells on histology. Nerve damage is early, severe and asymmetric. Lepromatous leprosy shows the opposite—absent lepromin positivity, numerous lesions, high bacterial load. BB (mid-borderline) is immunologically unstable with intermediate features.

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

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Written and medically reviewed by the StethoPrep medical team.