Tuberculosis and the atypical pneumonia syndrome.

Literature over the last 30 years has warned of the atypical or unusual characteristics of pulmonary TB. Shifts in the demographic distribution of the disease in the US are ascribed in part to the occurrence of HIV disease outbreaks in group settings, and to recent influxes of immigrants from developing countries. Unsuspected pulmonary TB is particularly common among the elderly. Socioeconomic categories not traditionally thought of as being high risk also are affected. In the low-risk setting, TB can be treacherous because misdiagnosis is likely. Tuberculosis is a great mimicker, and it can appear to be any acute community-acquired pneumonia such as atypical pneumonia. Symptoms and signs are few. A high index of awareness is therefore essential. The approach to atypical pneumonia emphasizes the need to include TB in the differential diagnosis to be aware of the total disease spectrum of TB and understand the risk factors. The atypical pneumonia syndrome is only a portion of the clinical spectrum of TB.