ABSTRACT
The differential diagnosis of the vasculitic syndromes includes many diverse disorders that result in organ ischemia, localized inflammation, and/or constitutional symptoms. While acute or subacute multisystem dysfunction should heighten concern for the presence of a vasculitic syndrome, nonvasculitic diseases can also present with involvement of multiple organ systems. Conversely, systemic vasculitis can manifest with involvement of a single anatomical region or organ. The pattern of expression of a specific vasculitic disorder may evolve or change over periods of time, independently of therapeutic interventions. For all of these reasons, and the continued controversy over diagnostic criteria, it is difficult at present to devise an evidence-based algorithmic approach to diagnosis, or even accurately describe the operating characteristics of many of the diagnostic tests we utilize. As a general principle, pathological documentation of vasculitis should be pursued whenever feasible. The possibility of a primary infectious or malignant disorder producing the vasculitis should also be considered. Serological or angiographic studies may support the clinical diagnosis of a primary vasculitic syndrome, but should not supplant efforts to exclude alternative diagnoses or document the presence and histological pattern of vasculitis. The clinician's ability to confidently diagnose a specific primary vasculitic syndrome is plagued by (I) frequent overlap of clinical patterns of disease among the different syndromes, especially early in the course of the illness; (2) difficulty in obtaining histopathology that is "diagnostic" of a single specific vasculitic syndrome; (3) lack of unequivocally diagnostic serological tests; (4) limited understanding of the role that viral and other infectious agents play in the development of some forms of vasculitis; and (5) limitations in our ability to delineate an ideal classification system. Nonetheless, the physician caring for patients with severe multisystem illnesses must quickly define the nature of the disease process. Either delayed or inappropriately aggressive therapeutic intervention may put the patient at risk for an adverse outcome.
