Diagnosis of Ocular Tuberculosis: A Role for New Testing Modalities?

Abstract

Tuberculosis (TB) is a disease caused by the acid-fast bacillus (AFB) Mycobacterium tuberculosis. TB usually affects the lungs [pulmonary TB (PTB)], but it can also affect any other part of the body [extrapulmonary TB (EPTB)]. EPTB with no evidence of pulmonary involvement accounted for 21.1% of those with TB in 2005, which represents an increase from 16% in 1992. The increase in the proportion of TB cases that are HIV coinfected has contributed to this increase in EPTB. The general symptoms of TB include weakness, weight loss, fever, and night sweats. Symptoms of PTB may also include coughing, chest pain, and hemoptysis. Symptoms of EPTB depend on the area affected. TB is spread from person to person through the air when a person with PTB coughs, sneezes, or speaks. Persons who breathe in the air containing M. tuberculosis can become infected asymptomatically; this is called latent TB infection (LTBI). It is estimated that one-third of the world’s population has LTBI. LTBI is not contagious, but about 5% of persons with LTBI (about 100 million people) will develop TB disease in the future. Progression of LTBI to TB is more common among those with compromised immune systems, those who were recently infected with M. tuberculosis, and people with certain medical conditions. Progression of LTBI to TB can be prevented with treatment such as 9 months of isoniazid.