ABSTRACT
Primary tuberculosis (TB) is the disease that occurs when there is no existing immune response to Mycobacterium tuberculosis. Material from the primary focus may then reach draining mediastinal lymph nodes, where mycobacterial antigens can be presented by dendritic cells to engage specific immunity. The combination of the primary focus and an enlarged mediastinal lymph node, containing the germinal centers where T and B cells proliferate, is termed the primary complex. The primary focus may have indistinct edges; subsequent healing with calcification leads to a clearly defined small nodule. Pleural effusions are related to a primary focus close to the pleura, such that the inflammatory response causes fluid to accumulate within the pleural space. The tissue destruction associated with cavitating post-primary TB, e.g., bronchiolar erosion with necrosis of adjacent blood vessels, Rasmussen's aneurysm and post-tuberculous bronchiectasis may cause massive hemoptysis, as can an aspergillomn.
