A rare case of tuberculosis verrucosa cutis on the buttocks

Mycobacterium tuberculosis infection remains a serious health concern in Taiwan. It most commonly affects the lungs, but any organ can be involved. Cutaneous tuberculosis (TB) is a relatively rare manifestation of TB infection, consisting only 1% to 2% of all extrapulmonary TB cases.1, 2 We herein report a case of tuberculosis verrucosa cutis presenting on the buttocks. A 51-year-old Taiwanese masonry worker with alcoholic liver cirrhosis and hepatocellular carcinoma presented to our dermatology outpatient department due to an enlarging verrucous plaque over the buttocks noted for 2 years (Figure 1A). The lesion started as a scaly plaque over the buttocks and the patient received treatment at a local clinic under the diagnosis of tinea corporis. However, the lesion gradually enlarged and became verrucous. Painful ulceration with serous discharge was also presented (Figure 1B). There were no obvious signs of infection. His laboratory data were within normal limits and chest radiography showed no obvious abnormalities. Skin biopsy was done at the border of the lesion. Histopathological examination showed pseudoepitheliomatous hyperplasia with dermal granulomatous inflammation composed of epithelioid histiocytes and mixed inflammatory cells (Figure 1C). Numerous Langerhans giant cells were identified in the granulomas (Figure 1C). Although Periodic Acid-Schiff staining, Grocott methenamine-silver staining, and Ziehl–Neelsen staining failed to identify any microorganism or acid-fast bacilli (AFB), tissue culture and polymerase chain reaction (PCR) both showed positive results for M. tuberculosis. Considering the clinical presentation and tissue culture results, a diagnosis of tuberculosis verrucosa cutis was made. Much improvement of the lesion was noted after treatment with rifampicin, isoniazid, ethambutol, and clarithromycin. Cutaneous TB is a relatively uncommon form of TB infection and remains a diagnostic challenge due to its diverse clinical manifestation, which depends on the immune status of the host and previous sensitization to the pathogen.1-3 Tuberculosis verrucosa cutis is a paucibacillary subtype of cutaneous TB caused by exogenous inoculation of M. tuberculosis or Bacillus Calmette-Guérin in previously sensitized individuals with moderate to high immunity.2, 3 Clinically, tuberculosis verrucosa cutis commonly occurs at sites prone to trauma such as the distal extremities and the buttocks.2, 3 It usually presents as a hyperkeratotic verrucous plaque with irregular boarders but can mimic various other cutaneous condition such as verruca vulgaris, verrucous carcinoma, cutaneous mycetoma, hyperkeratotic lupus vulgaris, hypertrophic lichen planus, or tertiary syphilis, leading to delayed diagnosis.2, 3 Owing to its paucibacillary nature, AFB are rarely identified by tissue Ziehl-Neelsen staining, making it difficult to diagnose without tissue culture or PCR.4, 5 The treatment of cutaneous TB is generally similar to that of pulmonary TB and surgical intervention may be beneficial in cases with localized infection.1-3 All authors declare no conflict of interest.