A 30-year-old man presents with lupus vulgaris — an apple-jelly nodule on the cheek. Which investigation best confirms the diagnosis and also helps assess the extent of systemic disease?

• A Ziehl-Neelsen stain of skin smear
• B ELISA for anti-mycobacterial antibodies
• C Culture on LJ medium alone
• D Mantoux test with chest radiograph and histopathology of biopsy ✓

Explanation

Lupus vulgaris is the most common form of cutaneous TB in India. AFB are scanty on smear. The combination of a strongly positive Mantoux (>15 mm), histopathology showing tuberculous granulomas with Langhans giant cells and caseous necrosis, and a chest X-ray (to assess pulmonary TB) provides the most comprehensive diagnostic and staging information. Culture confirms species but takes weeks. The condition can lead to squamous carcinoma if neglected.

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.