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Giant cell arteritis (GCA)—also known as temporal arteritis—is the most common form of systemic vasculitis in adults. GCA is a panarteritis that occurs almost exclusively in older people and preferentially affects the extracranial branches of the carotid artery. The most feared complication of GCA is blindness, which usually can be prevented by early diagnosis and treatment with glucocorticoids. Polymyalgia rheumatica (PMR) is an aching and stiffness of the shoulders, neck, and hip-girdle area that can occur with GCA, or more commonly, by itself.

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GCA

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  • Headache, polymyalgia rheumatica, jaw claudication, visual symptoms, PMR.
  • Temporal artery biopsy is the gold standard for diagnosis.

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PMR

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  • Stiffness and aching of the shoulders, neck, and hip region.
  • Diagnosis is clinical.
  • Elevated erythrocyte sedimentation rate (ESR).

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Although the causes of PMR and GCA are unknown, the disorders share many risk factors and probably mechanisms of pathogenesis. Age is the greatest risk factor for developing either condition. Almost all patients who have GCA are older than 50 years (the average age of onset is 72). The incidence of GCA rises from 1.54 cases per 100,000 people in the sixth decade to 20.7 per 100,000 in the eighth decade.

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PMR is 2–4 times more common than GCA, and its incidence also rises with age. Women are twice as likely as men to have GCA or PMR. Both conditions develop most often in Scandinavians and in Americans of Scandinavian origin. GCA rarely develops in black men.

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GCA and PMR are associated with the same human leukocyte antigen genes as those seen in patients with rheumatoid arthritis (ie, human leukocyte antigen-DR4 variants *0401 and *0404). The pathogenesis of GCA appears to be initiated by T cells in the adventitia responding to an unknown antigen, which prompts other T cells and macrophages to infiltrate all layers of the affected artery and to elaborate cytokines that mediate both local damage to the vessel and systemic effects (Figure 30–1). The differential expression of inflammatory cytokines may explain the clinical subsets seen in GCA. Patients with the highest levels of interleukin-6, for example, are more likely to have fever and less likely to experience blindness. MRI and ultrasonography show that PMR is caused by inflammation of the synovial lining of the bursa and joints around the neck, shoulders, and hips.

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Figure 30–1.
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Giant cell arteritis. Temporal artery biopsy showing endothelial proliferation, fragmentation of internal elastic lamina, and infiltration of the adventitia and media by inflammatory cells. Giant cells are especially well seen in the inset. (Reproduced, with permission, from Hellmann DB. Vasculitis. In: Stobo J, et al, eds. Principles and Practice of Medicine. Appleton & Lange; 1996.)

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Although GCA may develop later in some patients with PMR, patients who have only PMR are not at risk for losing their ...

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