A histopathological section from a leprosy patch shows an unbroken grenz zone, solid-staining bacilli in foamy macrophages (Virchow cells), and no lymphocytic infiltration. The Ridley-Jopling classification for this lesion is:

• A Tuberculoid (TT)
• B Lepromatous leprosy (LL) ✓
• C Borderline tuberculoid (BT)
• D Borderline lepromatous (BL)

Explanation

Lepromatous leprosy (LL) histopathology classically shows: (1) a clear grenz zone (Unna's band) of uninvolved papillary dermis, (2) foamy macrophages (Virchow cells) loaded with solid-staining bacilli, and (3) absence of significant lymphocytic infiltration — reflecting deficient T-cell immunity. In TT, the granuloma reaches the epidermis (no grenz zone), has epithelioid cells and giant cells, and bacilli are absent. BL shows partial destruction of grenz zone and some lymphocytes.

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

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Written and medically reviewed by the StethoPrep medical team.