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| Fig. 30.4 Lupus vulgaris. A, Red-brown plaque on nasal tip. B, Lupus vulgaris with squamous cell carcinoma. |
Lupus vulgaris is a chronic progressive form of cutaneous tuberculosis that originates from another site and involves the skin or mucous membranes via contiguous, lymphatic, or hematogenous spread. In 40% of patients, there is underlying lymphadenitis, and 10% to 20% have underlying pulmonary involvement. The primary skin lesion is an asymptomatic macule or papule that is brown-red in color and has a soft gelatinous consistency (Fig. 30-4A). Diascopy, a test where a glass slide is gently pressed against the skin lesion, may be helpful in diagnosing lupus vulgaris. Lupus vulgaris lesions have a characteristic “apple jelly” color with this technique. Squamous cell carcinoma arising in a longstanding lesion is the most serious complication (Fig. 30-4B).
