The term vasculitis indicates the presence of inflammation in a blood vessel wall. The inflammatory infiltrate may be one that is predominantly neutrophilic, eosinophilic, or mononuclear. Perivasculitis describes inflammation around the blood vessel wall but without mural involvement. Vasculopathy , a broader term, indicates an abnormality of blood vessels that may be inflammatory, degenerative, or may result from intimal proliferation.
The vasculitides are the most difficult of all rheumatic diseases to classify. Traditionally, vasculitis syndromes have been categorized according to features that include clinical phenotype, the predominant size of the involved vessels, or the histopathology of the involved vessel. Within such a framework, in 1990 a committee of the American College of Rheumatology (ACR) provided formal classification criteria for many, but not all, individual types of vasculitis. In 2012, the International Chapel Hill Consensus Conference (CHCC 2012) updated the 1994 consensus recommendations (CHCC 1994) on the names of diseases, preferred abbreviations, and disease definitions ( Table 32-1 ). CHCC 2012 retained the ACR framework for categories of vasculitis based on the size of predominantly affected blood vessels defined as follows. Large-vessel vasculitis (LVV) involves arteries outside organs, including muscles, nerves, kidneys, and skin; medium-vessel vasculitis (MVV) involves the main visceral arteries and their branches; small-vessel vasculitis (SVV) involves intraparenchymal arteries, arterioles, capillaries, and venules. Variable-vessel vasculitis (VVV) involves vessels (arteries, veins, capillaries) of any size and includes Behçet disease and Cogan syndrome. Also added are categories of single organ vasculitis (which includes isolated central nervous system vasculitis), vasculitis associated with systemic disease (such as systemic lupus erythematosus) and vasculitis associated with a probable etiology (such as hepatitis or drug-induced vasculitis). The most notable addition has been the incorporation of the presence or absence of antineutrophil cytoplasmic antibody (ANCA) within the classification framework, and thus small vasculitis is subcategorized into immune complex and ANCA-associated vasculitis. Subcategorization according to histopathology (e.g., granulomatous versus nongranulomatous) has not been retained because of the limited consistency of histopathological findings. The use of eponyms have also been phased out, particularly where a noneponymous replacement could reflect some pathophysiological specificity. Thus, Wegener granulomatosis, Churg–Strauss syndrome, and Henoch–Schönlein purpura have been replaced, respectively, with the terms granulomatosis with polyangiitis (GPA), eosinophilic granulomatosis with polyangiitis (EGPA), and IgA vasculitis.
|Large-vessel vasculitis (LVV) *|
|Giant cell (temporal) arteritis (GCA)||Granulomatous arteritis of the aorta and its major branches with a predilection for the extracranial branches of the carotid artery. It often involves the temporal artery. Usually occurs in patients older than 50 years of age and is often associated with polymyalgia rheumatica . †|
|Takayasu arteritis (TAK)||Granulomatous inflammation of the aorta and its major branches. Usually occurs in patients much younger than 50 years of age .|
|Medium-vessel vasculitis (MVV) *|
|Polyarteritis nodosa (PAN)||Necrotizing inflammation of medium-sized or small arteries without glomerulonephritis or vasculitis in arterioles, capillaries, or venules and not associated with ANCAs.|
|Kawasaki disease (KD)||Arteritis involving large, medium-sized, and small arteries associated with the mucocutaneous lymph node syndrome. Coronary arteries are often involved. Aorta and veins may be affected. Usually occurs in children .|
|Small-vessel vasculitis (SVV) *|
|ANCA-associated vasculitis (AAV)|
|Granulomatosis with polyangiitis (GPA)||Granulomatous inflammation involving the respiratory tract associated with necrotizing vasculitis affecting small- to medium-sized vessels. Necrotizing glomerulonephritis is common .|
|Eosinophilic granulomatosis with polyangiitis (EGPA)||Eosinophilic and granulomatous inflammation involving the respiratory tract accompanied by necrotizing vasculitis affecting small- to medium-sized vessels associated with asthma and eosinophilia.|
|Microscopic polyangiitis (MPA)||Necrotizing vasculitis with few or no immune deposits, affecting small vessels. Necrotizing arteritis involving small- and medium-sized arteries may be present. Necrotizing glomerulonephritis is common. Pulmonary capillaritis often occurs .|
|Immune complex small vessel vasculitis|
|IgA vasculitis (Henoch–Schönlein) (IgAV)||Vasculitis characterized by immunoglobulin A–dominant immune deposits affecting small vessels. Typically involves skin, gut, and glomeruli. Arthralgias and arthritis are common .|
|Cryoglobulinemic vasculitis (CPV)||Vasculitis with cryoglobulin immune deposits affecting small vessels associated with cryoglobulinemia. Skin and glomeruli are often involved .|
|Antiglomerular basement membrane (anti-GBM) disease||Vasculitis affecting pulmonary and renal capillaries with deposition of antiglomerular basement membrane antibodies.|
|Hypocomplementemic urticarial vasculitis||Associated with anti-C1q antibodies. Affects kidney, joints, lungs, and eyes.|
|Variable vessel vasculitis (VVV) |
Behçet disease (BD)
Cogan syndrome (CS)
|Affects arteries and veins with thrombosis, arteritis, and arterial aneurysms. Oral and/or genital aphthous ulcers, and can involve skin, eyes, joints, and central nervous system. |
Affects small, medium, or large arteries; aortitis, aortic, and mitral valvulitis.
|Single organ vasculitis (SOV)|
|Cutaneous leukocytoclastic angiitis||Vasculitis. Isolated cutaneous leukocytoclastic angiitis without systemic vasculitis or glomerulonephritis.|
|Cutaneous arteritis||Cutaneous vasculitis not associated with systemic vasculitis.|
|Primary central nervous system vasculitis||CNS vasculitis not associated with systemic vasculitis.|
|Isolated aortitis||Aortitis not associated with systemic vasculitis.|
* Large vessels: aorta and its larger branches directed toward major anatomic regions; medium vessels: renal, hepatic, coronary, and mesenteric arteries; small vessels: venules, capillaries, arterioles, and intraparenchymal distal arteries and arterioles.
The CHCC 2012 nomenclature and the definitions do not provide diagnostic and classification criteria. Therefore, the 1990 ACR criteria, derived primarily from adult-patient data, remains the most widely used system for classifying patients with vasculitis. These ACR criteria have limited usefulness when applied to children with chronic vasculitis and result in a significant proportion being described as unclassifiable. A pediatric adaptation of the ACR criteria, taking into account common pediatric manifestations and the presence of ANCA, was developed by consensus by a group of pediatric experts and reported in 2006 ( Box 32-1 ). Proposed criteria for four diseases (GPA, Takayasu arteritis [TAK], polyarteritis nodosa [PAN], and Henoch–Schönlein purpura [HSP]) were subsequently tested and improved upon using a cohort of pediatric patients. The final validated criteria had improved sensitivity when compared with the ACR criteria and were subsequently published in 2010, after having been endorsed by the European League Against Rheumatism, the Pediatric Rheumatology International Trial Organization, and the Pediatric Rheumatology European Society (EULAR/PRINTO/PRES). Unfortunately, these criteria retain some inherent limitations of the ACR criteria that have also been recognized in the adult literature. Specifically, the lack of any criteria for microscopic polyangiitis (MPA) has led to difficulties in discriminating GPA patients from MPA patients (see Chapter 36 ). This conundrum has led, on the one hand, to the convenient grouping of GPA and MPA in adult clinical trials under the rubric of ANCA-associated vasculitis (AAV). On the other hand, complex algorithms have been proposed or required to differentiate patients with the various types of AAV and PAN for study. Because of this and other classification inadequacies, the whole system for classifying vasculitis currently remains under scrutiny. The CHCC 2012 initiative provides a framework for developing and rigorously verifying new criteria. The Diagnostic and Classification of Vasculitis (DCVAS) prospective study is an international initiative launched in 2010 aiming to develop both revised classification criteria and a validated set of diagnostic criteria for systemic vasculitis in adult patients. This will have implications for the diagnosis and classification of pediatric patients that will be evaluated in an integrated Pediatric Vasculitis Initiative (PedVas).