Lupus vulgaris with squamous cell carcinoma.

Tuberculosis is still a significant problem in developing countries. Cutaneous forms of tuberculosis account for approximately 10% of all cases of extrapulmonary tuberculosis. Cutaneous tuberculosis may be because of true infection with Mycobacterium tuberculosis or because of tuberculids. Tuberculids are immunological reactions to haematogenously spread antigenic components of M. tuberculosis. True cutaneous tuberculosis may be because of inoculation or haematogenous spread of M. tuberculosis to the skin. Lupus vulgaris is the commonest form of true cutaneous tuberculosis. Other forms of true cutaneous tuberculosis are tuberculous chancre, tuberculosis verrucosa cutis, scrofuloderma, periorificial tuberculosis and miliary tuberculosis of the skin. Lupus vulgaris is usually chronic and progressive. It occurs in patients with moderate to high immunity against M. tuberculosis as evidenced by strongly positive tuberculin test. Long-standing cases of lupus vulgaris may be complicated by squamous cell carcinoma (SCC). We describe a patient who had undiagnosed lupus vulgaris for 35 years until she developed SCC on the lesion of lupus vulgaris.