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Spring 2020, Vol. 28 No. 1

Hong Kong J. Dermatol. Venereol. (2020) 28, 43


Answers to Dermato-venereological Quiz

Answers to Dermato-venereological Quiz

CMT Cheung 張敏彤, AWS Chan 陳慧詩, PCL Choi 蔡祥龍

  1. Clinical differential diagnoses include verruca vulgaris, deep fungal infection (such as chromoblastomycosis, blastomycosis, coccidioidomycosis), atypical mycobacterial infection, tuberculosis verrucosa cutis, verrucous carcinoma and squamous cell carcinoma.
  2. Histopathological examination of the skin biopsy shows pseudoepitheliomatous hyperplasia, with mid and deep dermal aggregates of epithelioid histiocytes admixed with neutrophils, lymphocytes and plasma cells. Ziehl-Neelsen stain shows scanty acid-fast bacilli.
  3. The diagnosis is tuberculosis verrucosa cutis (TVC). Mycobacterium tuberculosis (MTB) complex was isolated from the patient's skin tissue culture. Tuberculosis verrucosa cutis is a type of paucibacillary cutaneous tuberculosis infection in a person with moderate to high immunity to M. tuberculosis. It is mostly caused by direct exogenous inoculation of tuberculosis into the skin. Patients usually present with an asymptomatic warty papule that gradually increases in size. The hands, ankles, knees and buttocks are the common sites of involvement.
  4. This case should be reported to Centre for Health Protection in Hong Kong as tuberculosis is a statutory notifiable disease. Tuberculosis verrucosa cutis should be treated with standard anti-tuberculosis regimen (i.e. rifampicin, isoniazid, ethambutol and pyrazinamide), and the treatment should be guided by culture sensitivity and clinical response.