In which type of leprosy is the pure neuritic (primary neuritic leprosy) form most commonly classified, and what is the characteristic histopathological finding in the nerve biopsy?

• A TT — well-formed epithelioid cell granulomas within the nerve ✓
• B BT — partial nerve granuloma with lymphocytic cuffing
• C LL — foamy macrophage collections within perineural tissue
• D BL — fibrosis with mixed infiltrate but no granuloma formation

Explanation

Pure neuritic leprosy without skin lesions is most commonly classified as TT or BT on nerve biopsy. In TT, nerve biopsy shows well-formed epithelioid cell granulomas with Langerhans giant cells within the nerve fascicles, causing severe nerve damage. The nerve architecture is destroyed. This form shows negative smears but strong cell-mediated immunity. It is important to biopsy the sural or radial cutaneous nerve in appropriate clinical suspicion.

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

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