What Causes Vasculitis?

Vasculitis refers to a group of disorders characterized by inflammation and damage to blood vessel walls. The underlying cause varies depending on the specific type of vasculitis, but in most cases, it results from an abnormal immune-mediated response—essentially, the body’s immune system mistakenly attacks its own blood vessels. This autoimmune reaction can be triggered by genetic predisposition, environmental exposures (such as certain infections—including hepatitis B or C, HIV, or bacterial pathogens like *Streptococcus*), or exposure to medications or illicit drugs.

In some forms—particularly those affecting small- or medium-sized vessels—vasculitis is strongly associated with antineutrophil cytoplasmic antibodies (ANCA), which activate neutrophils and promote vascular injury. Other subtypes may involve immune complex deposition (e.g., in cryoglobulinemic vasculitis or IgA vasculitis), complement activation, or direct endothelial injury from infectious agents or toxins.

While the precise initiating event remains unclear in many patients, research increasingly points to dysregulation across multiple immune pathways—including aberrant T-cell activation, cytokine imbalances (e.g., elevated IL-6, TNF-α), and loss of self-tolerance—as central to disease pathogenesis. Importantly, vasculitis is not a single disease but a heterogeneous spectrum encompassing over 20 distinct clinical entities, each with unique epidemiology, histopathologic features, and therapeutic implications.