Giant-cell vasculitis typically affects large arteries that have an elastic lamina
Most commonly, these vessels are part of the carotid artery or its branches. But this is a systemic disorder, and any large artery may be affected. Giant-cell arteritis is histologically characterized by features of a panarteritis. This panarteritis is accompanied by inflammatory, mononuclear infiltrates inside the vessel wall, which usually focus on the internal, elastic lamina. Multinucleated giant cells are typical. This pathophysiology suggests a cell-mediated immune response, probably specific for antigens in the elastic lamina. The pathophysiology is supported by distinct cytokine patterns; detection of increases in tumor necrosis factor, IL-6, IL-1β, IL-2 and IFN-γ; and identification of T lymphocytes expressing specific antigen receptors with restricted clonal expansion. Temporal arteritis or cranial arteritis occurs almost exclusively in individuals more than 50 years of age and is more common in Caucasian women of northern-European heritage. Familial aggregation and an association with select human leukocyte antigen (HLA) alleles, particularly HLA-DR4, support a genetic predisposition for the disease. Polymyalgia rheumatica, a syndrome accompanied by symmetrical musculoskeletal aching, often occurs with giant-cell vasculitis, but this condition may occur alone and is twice as common as giant- cell vasculitis.
The clinical symptom that makes giant-cell vasculitis likely to be encountered by allergists/immunologists is headache. This headache is easily confused with the other facial and cranial complaints that are sometimes attributed to sinus disease. The headache is often more severe than a patient’s prior headaches, is described as somewhat boring in character, and may be unilateral. Scalp pain, particularly with hair brushing or with chewing, are highly suggestive of the diagnosis. Other manifestations include fatigue, malaise, anorexia, weight loss, subjective fever, or sweats, along with pain in the axial and proximal muscle extremities. Initial physical findings are limited and include tenderness of the temporal artery and occasionally over one or more branches of the affected arteries. As with other vasculitic syndromes, ischemia is the major complication. In this case, ischemia often affects the ophthalmic arteries—with blindness from optic nerve ischemia being the most common and severe complication.
Laboratory findings include increased erythrocyte sedimentation rate, normochromic or slightly hypochromic anemia, increased gamma globulin and complement, elevated C-reactive protein, increased blood IL-6 concentration, and mildly abnormal liver-function. Most of these findings reflect a systemic response to release of inflammatory cytokines, particularly IL-1, IL-6, and tumor necrosis factor.
Diagnosis is usually confirmed by microscopic examination of a temporal artery segment (Figure 4). A biopsy of 3-5 cm of vascular tissue will optimize diagnostic potential. Bilateral biopsies slightly increase diagnostic yield. Treatment may be initiated for as long as a week to 14 days before biopsy without significantly modifying pathologic findings. This may be important to a clinician who might begin treatment before obtaining a biopsy to minimize the chance of irreversible blindness if the biopsy is postponed.
Treatment of giant-cell vasculitis is similar to that for other forms of complicated vasculitis, except that oral glucocorticoids alone are more likely to be sufficient. Treatment is usually initiated at 40-60 mg/day until the disease is controlled, as manifested by resolution of symptoms and normalization of blood abnormalities—particularly anemia and ESR. Tapering of the glucocorticoid therapy should be started as soon as possible to minimize systemic side effects, as treatment may be necessary for up to 2 years, usually on an every-other-day schedule. Weekly methotrexate has permitted a reduction or discontinuation of glucocorticoid therapy in 2 randomized trials, allowing control of the disease with limitation of side effects such as osteoporosis. Giant-cell vasculitis has fewer tendencies to relapse following remission compared to ANCA-positive vasculitis. Polymyalgia rheumatica is best treated with low-dose prednisone (usually 10-15 mg daily) for 6-12 months.
Allergists/immunologists frequently see hypersensitivity vasculitis associated with viral infection and drug allergy. A consideration of this syndrome often enters into the differential diagnosis between urticaria and urticarial vasculitis. Allergists/immunologists commonly encounter ANCA-positive vasculitis because these conditions affect the lung and upper airway. Churg Strauss vasculitis occurs in subjects with a history of asthma and is characterized by pulmonary infiltrates and eosinophilia. Wegener’s vasculitis and Churg Strauss vasculitis often result in a persistent sinusitis. Microscopic polyangiitis is also associated with pulmonary infiltrates and hemoptysis. Finally, the headache found in giant-cell vasculitis may be confused with sinusitis, introducing this condition into the differential diagnosis of individuals being evaluated for sinus complaints.
Assessment and treatment of vasculitis remains empirical because of the absence of known etiologies and pathophysiology. The value of combining oral glucocorticoid therapy with cyclophosphamide has stood the test of time in Wegener’s granulomatosis, but disease relapse and efforts to limit side-effects greatly spur our search for other therapies.
Many alternatives for vasculitis treatment are available but inadequate experience prevents definitive recommendations. Since vasculitic syndromes are relatively rare, our potential of gathering sufficient numbers of patients for double-blind trials is low. Therefore, each clinician must weigh risks against benefits in various treatment options without the advantage of definitive trial data. Treatment choices remain a challenge in managing subjects diagnosed with vasculitis.
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