How does vasculitis damage small blood vessels in connective tissue diseases?

In the context of connective tissue diseases, vasculitis damages small blood vessels primarily through the deposition of immune complexes within vessel walls. These complexes, formed by the combination of antibodies and antigens, trigger a cascade of injurious effects when they interact with complement, a component of the immune system.12

This process leads to inflammation and, in some cases, necrosis (tissue death) of the vessel walls. The damaged walls often accumulate deposits of a translucent, fibrin-like material known as fibrinoid. In conditions such as polyarteritis nodosa, this inflammation and necrosis can cause the vessel to dilate, potentially leading to the formation of small aneurysms.12

These vascular injuries are considered a hallmark of autoimmune diseases, where the body’s immune system mistakenly attacks its own tissues, resulting in the aggregation of lymphocytes and plasma cells at the sites of damage.2