A 16-year-old Indian boy presented with an 8-year history of an asymptomatic, slowly progressive skin lesion over the left knee. Examination showed a single, well-defined erythematous scaly plaque with crusting, and areas of atrophy and scarring (Figure 1A). the general examination was normal. The patient’s past medical history and family history were not significant. A tuberculin skin test was strongly positive (Figure 2). Incisional biopsy revealed multiple well-formed epithelioid granulomas with or without giant cells surrounded by lymphocytic infiltrates in the dermis (Figure 3). Ziehl-Neelson staining of the tissue section, mycobacterial culture of a tissue specimen, and polymerase chain reaction for Mycobacterium tuberculosis were negative. Based on the clinicopathologic findings, a diagnosis of lupus vulgaris was made. The patient was treated with antituberculous therapy (rifampicin, isoniazid, pyrazinamide, and ethambutol) for 6 months. At the end of treatment, the lesion had healed well, leaving an atrophic, wrinkled scar (Figure 1B).
Lupus vulgaris is a chronic, progressive paucibacillary form of cutaneous tuberculosis. Criteria for diagnosis are variable. Tuberculin skin testing is usually positive.1 Analysis of a biopsy specimen should include histopathology, tissue smear, bacteriologic cultures, and polymerase chain reaction, but may be negative, as in this case of paucibacillary disease reminiscent of tuberculoid leprosy.2 Assessment for pulmonary and extrapulmonary tuberculosis should be done.3 Complications may occur, including secondary bacterial infections, mutilation, destruction, scarring, and joint contractures.3,4 Cutaneous tuberculosis generally responds well to antituberculous treatment.2
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Santos JB, Figueiredo AR, Ferraz CE, Oliveira MH, Silva PG, Medeiros VL, 2014. Cutaneous tuberculosis: diagnosis, histopathology and treatment—part II. An Bras Dermatol 89: 545–555.
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