Reactivation TB
>> Friday, February 20, 2009
Postprimary TB results from either reactivation of a latent primary infection or, less commonly, from the repeat infection of a previously sensitized host. The term "postprimary" is preferred to "reactivation" when referring to the clinical diagnosis because firmly distinguishing recurrence from an antecedent infection is impossible in most cases. Approximately 10% of all infected patients are likely to develop reactivation, and the risk is highest within the first 2 years or during periods of immunosuppression.
Postprimary TB is typically a disease of adolescence and adulthood that results from reactivation of an initially contained infection by a TB complex mycobacterium. Pulmonary reactivation usually occurs in the apical and posterior segments of the upper lobes or in the superior segments of the lower lobes. This distribution may be related to the higher oxygen tension or the reduced perfusion and lymphatic clearance in these lung segments




