What are post mortem lesions associated with Tb characterized by?

The post mortem lesions associated with tuberculosis (Tb) are characterized by the presence of granulomas, which are specific types of inflammatory responses in the tissue where the bacteria have localized. These granulomas are clusters of immune cells that form when the body tries to contain an infection, such as that caused by the Mycobacterium tuberculosis bacteria. The formation of these lesions is significant because they serve as a hallmark of tuberculosis infection, reflecting how the body is attempting to manage and contain the disease process.

Granulomas in Tb typically consist of macrophages that transform into epithelioid cells and may become multinucleated giant cells in an effort to wall off the infection. As the condition progresses, these granulomatous lesions can undergo necrosis and can manifest as caseating (cheesy) necrosis, which is often observed during necropsy.

In contrast, pneumonic cavities represent a more severe and advanced stage of lung damage and are not characteristic of the initial post mortem findings of Tb. Fibrosis of lung tissue may be seen in chronic cases but does not specifically define the hallmark lesions of tuberculosis. Clear lung tissue without inflammation would generally not occur in the presence of an active infection like tuberculosis, as there is typically a response from the immune