Tuberculosis verrucosa cutis presenting as a chronic verrucous foot plaque: a diagnostic quandary

Abstract

Cutaneous tuberculosis (CTB) is a rare manifestation of extra-pulmonary tuberculosis; tuberculosis verrucosa cutis (TBVC) presents as a slowly enlarging verrucous lesion, often misdiagnosed due to its atypical presentation. A 22-year-old male driver presented with a 2-year history of a pruritic, intermittently discharging, well-defined verrucous plaque with central depigmentation over the medial right foot, gradually enlarging to ~7×5 cm. KOH and fungal cultures were negative; Tuberculin skin test was strongly positive. Histopathology revealed pseudoepitheliomatous hyperplasia, mid-dermal well-formed tuberculoid granulomas with Langhans giant cells and neutrophilic microabscesses. No organisms were seen. Biopsy samples for cartridge based nucleic acid amplification test (CBNAAT) documented mycobacterium tuberculosis (MTB) genome. Imaging ruled out bone involvement. Diagnosis of TBVC was made, and anti-tuberculosis (ATT) therapy was initiated with clinical improvement. This case underscores the importance of considering TBVC in chronic verrucous skin lesions, particularly in endemic areas, and highlights the diagnostic value of histopathology and CBNAAT testing. The diagnostic puzzle was resolved using nucleic acid amplification testing of the biopsy sample, which should be considered in all skin lesions suspected of tuberculosis.