Miliary tuberculosis: new insights into an old disease.

Miliary tuberculosis is a potentially lethal form of tuberculosis resulting from massive lymphohaematogeneous dissemination of Mycobacterium tuberculosis bacilli. The emergence of the HIV/AIDS pandemic and widespread use of immunosuppressive drugs has changed the epidemiology of miliary tuberculosis. Impaired cell-mediated immunity underlies the disease's development. Clinical manifestations are non-specific and typical chest radiographic findings may not be seen until late in the course of the disease. Atypical presentations--eg, cryptic miliary tuberculosis and acute respiratory distress syndrome--often delay the diagnosis. Several laboratory abnormalities with prognostic and therapeutic implications have been described, including pulmonary function and gas exchange impairment. Isolation of M tuberculosis from sputum, body fluids, or biopsy specimens, application of molecular methods such as PCR, and histopathological examination of tissue biopsy specimens are useful for the confirmation of diagnosis. Although response to first-line antituberculosis drugs is good, evidence regarding optimum duration of treatment is lacking and the role of adjunctive corticosteroid treatment is unclear.