Tuberculous Cellulitis: Diseases Behind Cellulitislike Erythema
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.
Cutaneous tuberculosis generally is classified into 4 types according to the mechanism of disease acquisition: (1) inoculation from an exogenous source, (2) endogenous cutaneous spread contiguously or by autoinoculation, (3) hematogenous spread to the skin, and (4) tuberculids. In our case, it was suspected that the cellulitislike erythema may have been caused by hematogenous spread from pulmonary tuberculosis. Considering that negative reactions to purified protein derivative (tuberculin) skin tests often are observed in cases of miliary tuberculosis (widespread dissemination of M tuberculosis to 2 or more organs via hematogenous spread), we suspected that our patient could proceed to miliary tuberculosis; in fact, a case was reported in which miliary tuberculosis emerged approximately 3 weeks after the onset of erythema,13 as observed in the present case. Therefore, erythema in the setting of tuberculosis may be a predictor of miliary tuberculosis. The types of cutaneous lesions caused by tuberculosis infection also are dependent on multiple host factors.2 Cutaneous tuberculosis with an atypical clinical appearance has become more common because of the increasing number of immunocompromised patients.17
In addition, most cases of cutaneous tuberculosis are not associated with pain. Generally, tuberculous cellulitis also causes nontender erythematous plaques or nodules.2 However, in some cases of tuberculous cellulitis, including our case, tender skin lesions have been reported.12-14 Therefore, this symptom is not a sensitive factor for differential diagnosis.
We suggest that tuberculous cellulitis should always be included in the differential diagnosis of a cellulitislike rash with or without pain if the skin lesion is not improved despite antibiotic therapy.
