Celebrating progress in the vasculitides, old and new

Introduction

Ahead of the 21st International Vasculitis Workshop and the Fifth International Symposium on IgG4-related Disease, The Lancet Rheumatology celebrates progress in research on the vasculitides by publishing a Series of detailed reviews on three major forms: antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, giant cell arteritis, and IgG4-related disease. We mark the occasion with two complementary Series reviews on each of these conditions. All three forms of vasculitis have witnessed substantial steps forward over the past twenty years in treatment, diagnosis, or both. Indeed, IgG4-related disease was recognised as a unique autoimmune disease barely twenty years ago and not classified properly as a variable-vessel vasculitis until last year.1

We split each form of vasculitis into two papers for the following reasons. First, all three diseases can be regarded as pathophysiological spectra that are polarised. Thus, anti-proteinase 3 (PR3) ANCA associated vasculitis resides at one end of the disease spectrum and anti-myeloperoxidase (MPO) ANCA-associated vasculitis at the other.2,3 Similarly, cranial giant cell arteritis and large-vessel giant cell arteritis occupy the two ends of the giant cell arteritis spectrum,4,5 and proliferative as opposed to fibrotic IgG4-related disease claim comparable spaces in IgG4- related disease.6,7

It is important to acknowledge that for all three diseases, the spectra are marked by substantial overlap in the middle. For example, both PR3-ANCA-associated vasculitis and MPO-ANCA-associated vasculitis involve the alveolar capillaries, renal glomeruli, the skin, and peripheral nerves in ways that are essentially identical. Furthermore, a high proportion of patients with cranial giant cell arteritis could be shown to have large-vessel disease if appropriate imaging studies are done. In addition, evidence of fibrosis is present in all forms of IgG4-related disease by the time the disease is recognised, regardless of whether a patient is identified as belonging to the proliferative subset or the fibrotic subset.

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