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Vasculitis
Vasculitis SALAHUDDIN KAZI University of Texas Southwestern Medical Center, Dallas
predominantly seen in individuals from the Far East and Southeast Asia. The medium- and small-vessel vasculitides (polyarteritis nodosa and microscopic polyangiitis, Wegener's granulomatosis, and ChurgÿStrauss syndrome) are all relatively uncommon. Kawasaki disease primarily occurs in children under the age of 5 years. HenochÿSchoÈnlein purpura is the most common type of vasculitis in children and is relatively infrequent in adults. Cutaneous leukocytoclastic vasculitis is relatively common and frequently seems to be precipitated by the use of medications.
antineutrophil cytoplasmic antibodies Proteins directed against cytoplasmic neutrophil antigens such as proteinase 3 and myeloperoxidase; useful in the diagnosis of small-vessel vasculitis. Janeway lesion Painless, macular lesions on the palms and soles, characteristic of infective endocarditis. oligoarthritis Form of arthritis that involves more than one but a relatively small number of joints. Osler node A tender, raised, cutaneous lesion, typically on the ®nger pads; characteristic of infective endocarditis.
Vasculitis is de®ned pathologically as a vessel wall lesion characterized by the presence of leukocytes, with reactive damage to mural vascular structures resulting in tissue ischemia and necrosis. Clinically, vasculitis refers to syndromes resulting from such local, regional, or systemic in¯ammation and necrosis of blood vessels. Vasculitis may occur in the context of a well-de®ned disease such as infective endocarditis (secondary vasculitis) or may be idiopathic. Secondary vasculitis is much more common than idiopathic vasculitis. Disorders that mimic clinical vasculitis include multiple cholesterol emboli syndrome and several occlusive vasculopathic disorders. Histologically, such disorders are notable for the absence of vasculitic changes. The term ``vasculopathy'' is often applied to such disorders.
ETIOLOGY AND PATHOGENESIS The systemic vasculitides are immune-mediated in¯ammatory diseases for which the precise etiology is unclear. These diseases may be triggered by infection, with the release of proin¯ammatory cytokines and up-regulation of leukocyte adhesion molecules in an uncontrolled manner. Several factors appear to determine the size of vessel involved, the subsequent in¯ammatory responses, and systemic manifestations. These include the nature of the antigen involved, factors modulating endothelial cell activation, and other components of the in¯ammatory cascades, including cytokines, costimulatory molecules, and intracellular activation pathways. The end result is disruption of vessel integrity, producing clinical signs and symptoms of tissue ischemia. Giant cell arteritis appears to be a T-cell-mediated disease. Macrophages produce interleukin-1, interleukin-6, and transforming growth factor-b and often become organized as multinucleated giant cells under the in¯uence of interferon g. Takayasu's arteritis is also a granulomatous polyarteritis in which CD8 T cells have been identi®ed as the major cell type. Several candidate organisms have been associated with Kawasaki syndrome. It is speculated that toxins may act as superantigens. Polyarteritis nodosa is an immune complex vasculitis and has been reported in association with hepatitis B virus in some cases. Wegener's granulomatosis, microscopic polyangiitis, and ChurgÿStrauss syndrome have been referred to as the antineutrophil
CLASSIFICATION The idiopathic or primary systemic vasculitides are a heterogeneous group of diseases with frequent clinical and pathologic overlap. Classi®cation is based on vessel size, clinical features, and histology (Table I). Three main categories are recognized based on vessel size (large, medium, and small) and are further subclassi®ed based on clinical and histologic characteristics.
EPIDEMIOLOGY Although the causes of vasculitis are largely unknown, epidemiologic data have suggested roles for geographic, genetic, and environmental factors. Giant cell arteritis is the most common vasculitis in older individuals from North America and Europe. Takayasu's arteritis is
Encyclopedia of Gastroenterology
600
Copyright 2004, Elsevier (USA). All rights reserved.
predominantly seen in individuals from the Far East and Southeast Asia. The medium- and small-vessel vasculitides (polyarteritis nodosa and microscopic polyangiitis, Wegener's granulomatosis, and ChurgÿStrauss syndrome) are all relatively uncommon. Kawasaki disease primarily occurs in children under the age of 5 years. HenochÿSchoÈnlein purpura is the most common type of vasculitis in children and is relatively infrequent in adults. Cutaneous leukocytoclastic vasculitis is relatively common and frequently seems to be precipitated by the use of medications.
antineutrophil cytoplasmic antibodies Proteins directed against cytoplasmic neutrophil antigens such as proteinase 3 and myeloperoxidase; useful in the diagnosis of small-vessel vasculitis. Janeway lesion Painless, macular lesions on the palms and soles, characteristic of infective endocarditis. oligoarthritis Form of arthritis that involves more than one but a relatively small number of joints. Osler node A tender, raised, cutaneous lesion, typically on the ®nger pads; characteristic of infective endocarditis.
Vasculitis is de®ned pathologically as a vessel wall lesion characterized by the presence of leukocytes, with reactive damage to mural vascular structures resulting in tissue ischemia and necrosis. Clinically, vasculitis refers to syndromes resulting from such local, regional, or systemic in¯ammation and necrosis of blood vessels. Vasculitis may occur in the context of a well-de®ned disease such as infective endocarditis (secondary vasculitis) or may be idiopathic. Secondary vasculitis is much more common than idiopathic vasculitis. Disorders that mimic clinical vasculitis include multiple cholesterol emboli syndrome and several occlusive vasculopathic disorders. Histologically, such disorders are notable for the absence of vasculitic changes. The term ``vasculopathy'' is often applied to such disorders.
ETIOLOGY AND PATHOGENESIS The systemic vasculitides are immune-mediated in¯ammatory diseases for which the precise etiology is unclear. These diseases may be triggered by infection, with the release of proin¯ammatory cytokines and up-regulation of leukocyte adhesion molecules in an uncontrolled manner. Several factors appear to determine the size of vessel involved, the subsequent in¯ammatory responses, and systemic manifestations. These include the nature of the antigen involved, factors modulating endothelial cell activation, and other components of the in¯ammatory cascades, including cytokines, costimulatory molecules, and intracellular activation pathways. The end result is disruption of vessel integrity, producing clinical signs and symptoms of tissue ischemia. Giant cell arteritis appears to be a T-cell-mediated disease. Macrophages produce interleukin-1, interleukin-6, and transforming growth factor-b and often become organized as multinucleated giant cells under the in¯uence of interferon g. Takayasu's arteritis is also a granulomatous polyarteritis in which CD8 T cells have been identi®ed as the major cell type. Several candidate organisms have been associated with Kawasaki syndrome. It is speculated that toxins may act as superantigens. Polyarteritis nodosa is an immune complex vasculitis and has been reported in association with hepatitis B virus in some cases. Wegener's granulomatosis, microscopic polyangiitis, and ChurgÿStrauss syndrome have been referred to as the antineutrophil
CLASSIFICATION The idiopathic or primary systemic vasculitides are a heterogeneous group of diseases with frequent clinical and pathologic overlap. Classi®cation is based on vessel size, clinical features, and histology (Table I). Three main categories are recognized based on vessel size (large, medium, and small) and are further subclassi®ed based on clinical and histologic characteristics.
EPIDEMIOLOGY Although the causes of vasculitis are largely unknown, epidemiologic data have suggested roles for geographic, genetic, and environmental factors. Giant cell arteritis is the most common vasculitis in older individuals from North America and Europe. Takayasu's arteritis is
Encyclopedia of Gastroenterology
600
Copyright 2004, Elsevier (USA). All rights reserved.