A patient from Tamil Nadu presents with a pale hypoesthetic skin lesion with absent sweating and hair fall. Skin slit smear shows 0 AFB per 100 fields; biopsy shows epithelioid cell granulomas with Langhans giant cells and no detectable bacilli. Lepromin test (Mitsuda reaction at 28 days) shows a 10 mm indurated nodule. This patient is classified as:
- A Lepromatous leprosy (LL)
- B Tuberculoid leprosy (TT) ✓
- C Borderline tuberculoid (BT)
- D Mid-borderline (BB) leprosy
Explanation
Tuberculoid leprosy (TT) is the paucibacillary polar form with a strong Th1 immune response, evidenced by a strongly positive Mitsuda reaction (> 5 mm induration at 28 days), well-formed epithelioid granulomas, zero or undetectable bacteriological index (BI = 0), and clear skin lesions with absent sensation, sweating, and hair growth. LL shows a negative Mitsuda reaction, diffuse infiltration, and foamy macrophages (Virchow cells) packed with AFB. BT would show intermediate features with 1–4 patches. BB has poorly formed granulomas and weakly positive or negative Mitsuda.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
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Written and medically reviewed by the StethoPrep medical team.