20-16: Vasculitis Syndromes

Vasculitis is a heterogeneous group of disorders characterized by inflammation within the walls of affected blood vessels. The major forms of primary systemic vasculitis are listed in Table 20–11. The first consideration in classifying cases of vasculitis is the size of the major vessels involved: large, medium, or small. The presence of the clinical signs and symptoms shown in Table 20–12 helps distinguish among these three groups. After determining the size of the major vessels involved, other issues that contribute to the classification include the following:

• Does the process involve arteries, veins, or both?

• What are the patient’s demographic characteristics (age, sex, ethnicity, cigarette smoking status)?

• Which organs are involved?

• Is there hypocomplementemia or other evidence of immune complex deposition?

• Is there granulomatous inflammation on tissue biopsy?

• Are antineutrophil cytoplasmic antibodies (ANCA) present?

In addition to the disorders considered to be primary vasculitides, there are also multiple forms of vasculitis that are associated with other known underlying conditions. These “secondary” forms of vasculitis occur in the setting of chronic infections (eg, hepatitis B or C, subacute bacterial endocarditis), connective tissue disorders, IBD, malignancies, and reactions to medications. Only the major primary forms of vasculitis are discussed here.