Less than 20 years ago, the literature on vasculitis was primarily descriptive; reports were mostly from single centers and treatment outcomes were compared with historical controls. Few institutions had programs dedicated to treating patients with various forms of vasculitis, clinician-investigators who had bona fide expertise with these disorders were uncommon, the diseases were (and are) rare, and funding to support vasculitis research was limited.
Nonetheless, 50 years of earlier descriptive reports had revealed that certain forms of vasculitis were uniformly fatal without therapy. Consequently, studies with untreated controls were considered unethical. Despite these shortcomings, important information emerged from the pre-1990 era. For instance, several studies demonstrated that without treatment, diseases such as Wegener granulomatosis (WG)1 and microscopic polyangiitis (MPA)2 were often fatal within weeks to months. These sobering outcomes were especially common among patients who presented with pulmonary-renal syndromes, gastrointestinal ischemia, or central nervous system involvement. In addition, while glucocorticosteroid discovery and clinical application was a major breakthrough for many illnesses, it was not effective for the most severe types of systemic vasculitis. Many patients with critical organ involvement still died within months.