A patient presents with a chronic verrucous plaque on the buttock with central scarring. He has worked as a butcher. Biopsy shows tuberculous granuloma with caseation. Mantoux test is strongly positive (22 mm). ZN staining is negative. The diagnosis and route of infection are:

• A Tuberculosis verrucosa cutis (warty TB) — inoculation from exogenous source ✓
• B Lupus vulgaris — haematogenous spread
• C Scrofuloderma — direct extension from lymph node
• D Acute miliary tuberculosis cutis — haematogenous seeding

Explanation

Tuberculosis verrucosa cutis (warty tuberculosis) occurs by inoculation of M. tuberculosis from an exogenous source in previously sensitised (immune) individuals with high immunity. Occupational exposure (butchers, pathologists, veterinarians handling infected material) is classic. Lesions are verrucous plaques with central scarring, Mantoux strongly positive, bacilli are sparse (ZN often negative). Lupus vulgaris is the most common form of cutaneous TB, occurring via haematogenous or lymphatic spread, presenting as apple-jelly nodules. Scrofuloderma arises by direct extension from infected lymph nodes.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.