Giant cell arteritis, or temporal arteritis, is an inflammatory disorder of large and medium-sized arteries affected with granulomatous lesions containing T cells and macrophages. Vascular occlusion and tissue ischemia can result, often in the cranial arteries but also in the aorta and its larger branches. Vessel wall inflammation almost always occurs with systemic inflammation. Polymyalgia rheumatica, often coexistent with giant cell arteritis, consists of incomplete vessel wall inflammation with systemic inflammation causing myalgias of the neck, shoulders, and pelvis. Giant cell arteritis is diagnosed by temporal artery biopsy, while there is no specific test for poly-myalgia rheumatica. Weyand and Goronzy reviewed current knowledge about giant cell arteritis and polymyalgia rheumatica immunology and how this knowledge affects detection and treatment.

The two major immunopathogenetic processes are arterial wall infiltration by inflammatory cells, particularly T cells, caused by inappropriate activation of the adaptive immune system, and a separate systemic inflammation apparently caused by an excessively activated innate immune system. Clinical manifestations of giant cell arteritis can be abrupt or insidious. Common features such as headache and an elevated erythrocyte sedimentation rate (ESR) are nonspecific. More specific manifestations such as jaw claudication and diplopia are encountered in fewer than one third of cases. Other typical manifestations include blindness and polymyalgia rheumatica. Disease subtypes include cranial arteritis, large vessel arteritis or aortitis, systemic inflammatory syndrome with arteritis, and “isolated” polymyalgia rheumatica.

The diagnosis of giant cell arteritis includes measurement of acute phase reactants such as ESR and C-reactive protein. Interleukin-6 is being studied as a potentially more sensitive indicator of disease. Normocytic, normochromic anemia and thrombocytosis are common, and abnormal liver function test results, particularly elevated alkaline phosphatase levels, can occur. Normal acute phase reactant levels do not exclude giant cell arteritis, and temporal artery biopsy should be done when this disorder is suspected. Temporal artery biopsy looking for inflammatory infiltrate has the highest diagnostic yield and, when possible, should be performed before corticosteroid therapy to improve diagnostic yield. Imaging with radiography, computed tomography, or magnetic resonance angiography may be useful in patients with negative temporal biopsy by demonstrating lesions that are smoothly tapered at both ends and by detecting aneurysmal dilatations.

Treatment of giant cell arteritis employs a corticosteroid at an initial dosage of 1 mg per kg body weight of prednisone (see accompanying table). Dosing can be tapered every two weeks if clinical and laboratory signs of disease are decreasing. Studies of other immuno-suppressive agents have not shown any advantage over corticosteroids. The most common relapse manifestation of giant cell arteritis is polymyalgia rheumatica, which usually can be treated with small increases in the chronic corticosteroid dosage. Steroid treatment often can be discontinued before the two to four years required for the disease to burn itself out.

The authors conclude that current therapeutic regimens with corticosteroids have been successful in treating patients with giant cell arteritis based on the absence of increased mortality. Inflammation may continue to exist at a low level, but the risk for vascular complications is low. Bone-saving therapy should be offered to patients on chronic corticosteroid therapy because of their risk of osteopenia.