Presented next is a brief overview of several of the best-characterized vasculitides. Although each is presented as a distinct entity, it must be acknowledged that many cases of vasculitis lack a classic constellation finding or have overlapping features that may render classification difficult.
Giant cell (temporal) arteritis is a chronic inflammatory disorder, typically with granulomatous inflammation, that principally affects large-to small-sized arteries in the head. The temporal arteries are not more vulnerable than other arteries, but have leant their name to the disorder because the diagnosis is typically established by biopsy of these vessels. Vertebral and ophthalmic arteries, as well as the aorta (giant cell aortitis), are other common sites of involvement. Because ophthalmic artery vasculitis can lead to sudden and permanent blindness, affected individuals must be promptly diagnosed and treated promptly. It is the most common form of vasculitis among older adults in developed countries.
Giant cell arteritis likely occurs as a result of a T-cell– mediated immune response to an as-yet uncharacterized vessel wall antigen. Pro-inflammatory cytokines (especially TNF) and anti-EC antibodies also contribute. The characteristic granulomatous inflammation, an association with certain MHC class II haplotypes, and the excellent therapeutic response to steroids, all strongly support an immune etiology. The predilection for vessels of the head remains unexplained, although one hypothesis is that vessels in various parts of the body develop from distinct anlagen and may, therefore, express unique antigens.
http://ebooksmedicine.net
Temporal arteritis is rare before 50 years of age. Signs and symptoms may be vague and constitutional (e.g., fever, fatigue, weight loss) or take the form of facial pain or headache, most intense along the course of the superficial temporal artery, which is painful to palpation. Ocular symptoms (associated with involvement of the ophthalmic artery) abruptly appear in about 50% of patients; these range from diplopia to complete vision loss. Diagnosis depends on biopsy and histology; however, because the vascular inflammation is patchy, a negative biopsy result does not exclude the diagnosis. Corticosteroid or anti-TNF therapies are effective treatments.
MORPHOLOGYIngiantcellarteritis,thepathologicchangesarenotoriouslypatchyalongthelengthofaffectedvessels.Involvedarterialsegmentsexhibitnodularintimalthickening(andoccasionalthromboses)thatreducethevesseldiameterandcausedistalischemia.Thevastmajorityoflesionsexhibitgranulomatous inflammation withintheinnermediacenteredontheinternalelasticmembrane;thereisaninfiltrateoflymphocytesandmacrophages,withmultinucleategiantcells,andfragmentation of the internal elastic lamina (
Fig.10.23 ).Inupto25%ofcases,granulomasandgiantcellsareabsent,andlesionsexhibitonlyanonspecificpanarteritiswithamixedinfiltrateofacuteandchronicinflammation.Healingismarkedbyintimalthickening,medialthinningandscarring,andadventitialfibrosis.Character-istically,lesionsatdifferentstagesofdevelopmentareseenwithinthesameartery.
Takayasu arteritis is a granulomatous vasculitis of medium-and large-sized arteries characterized principally by ocular disturbances and marked weakening of the pulses in the upper extremities (hence the alternate name, pulseless disease). This disorder manifests with trans-mural scarring and thickening of the aorta—particularly the aortic arch and great vessels—with severe luminal narrowing of the major branch vessels (