HomeA proportion of those who are recently infected are unable to contain the infection, despite the stimulation of cell-mediated immunity, and there is progression to disease in a matter of months. Such early disease progression is a function of age and immunologic response; thus, disease is especially likely to occur in children 0-4 years of age and the immunocompromised.61–64 Local progression in the lung, or lymphohematogenous spread resulting in disseminated (miliary) disease and/or central nervous system disease, may occur as early as 2-to-6 months after infection in infants and severely immunocompromised hosts.61,64 Uncomplicated and asymptomatic lymph node disease (hilar or mediastinal lymphadenopathy without airway involvement) may also occur in the first 2-to-6 months of infection, although there is debate about whether this should be called active disease (see Chapter 9: Pediatric Tuberculosis).61,65
At 4-12 months after infection, early disease manifestations include complicated lymph node disease (airway compression, expansile caseating pneumonia, infiltration of adjacent anatomic structures), pleural disease (most commonly a lymphocyte-predominant exudative effusion) and peripheral lymphadenitis (usually in the cervical lymph nodes).61 In immunocompetent children and adolescents, early disease is more likely to manifest as intrathoracic adenopathy and in adults as a unilateral pleural effusion. In severely immunocompromised people of any age (e.g., those with advanced HIV or AIDS), early disease may manifest as intrathoracic adenopathy.66,67 Newly infected children who are 10 years of age or older (pubertal) or adolescents, may develop adult-type pulmonary disease (see below) or other types of extrapulmonary TB (for example bone and joint TB) within the first 8-24 months of infection.61,68
For purposes of disease reporting, most but not all patients with a diagnosis of TB made within 18-24 months of infection should be considered to have “primary” disease. Those newly infected persons in whom TB does not develop in this time period have three possible outcomes: they may remain infected indefinitely and never develop disease, they may naturally clear their infection over time or they may progress to active TB disease at a later date, beyond the first 18-24 months. The concept of disease tolerance provides further insight into the aforementioned host-pathogen interactions.
Switch To: Français