A molecular epidemiological assessment of extrapulmonary tuberculosis in San Francisco

The epidemiology of extrapulmonary tuberculosis ( TB) is not well understood. We studied all cases of extrapulmonary TB reported in San Francisco during 1991 - 2000 to determine risk factors for extrapulmonary TB and the proportion caused by recent infection. Isolates were analyzed by IS6110- based restriction fragment length polymorphisms analysis. There were 480 cases of extrapulmonary TB, of which 363 ( 76%) were culture positive; isolates were genotyped for 301 cases ( 83%). Multivariate analysis identified young age, female sex, and HIV infection as independent risk factors for nonrespiratory TB ( excluding pulmonary, pleural, and disseminated TB). Pleural TB was less common in HIV- seropositive persons and women than were nonrespiratory forms of extrapulmonary TB. Pleural TB is different from other forms of extrapulmonary TB and is associated with the highest clustering rate ( 35% of cases) of all forms of TB. This high rate of clustering occurs because pleural TB is often an early manifestation of recent infection.