RESUMEN
An 89-year-old man presented with an inflammatory erythematous plaque on the left thigh that closely mimicked cellulitis. Empiric therapies with ordinary antibiotics were not effective. A skin biopsy showed epithelioid cell granulomas throughout the dermis and subcutis. Ziehl-Neelsen stain revealed numerous acid-fast bacilli. Additionally, Mycobacterium tuberculosis was isolated from a skin biopsy specimen as well as gastric fluid and sputum cultures. He was diagnosed with tuberculous cellulitis with pulmonary tuberculosis. Cellulitis is a common disease seen by dermatologists; however, sometimes other diseases may masquerade as this banal illness. Among them, cutaneous tuberculosis should be excluded because of its clinical significance. Most cases of cutaneous tuberculosis are symptom free, but tuberculous cellulitis is sometimes painful. Therefore, cutaneous tuberculosis should always be considered in the differential diagnosis of a cellulitislike rash if the lesions do not respond to ordinary antibiotic therapy, especially in countries with a high incidence of tuberculosis.