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At a glance
- Giant cell arteritis (GCA) is often seen simultaneously with polymyalgia rheumatica (PMR.)
- Corticosteroid therapy is the mainstay treatment of GCA and PMR.
- When present, visual symptoms should be considered an ophthalmologic emergency.
- Biopsy of the artery in question is the gold standard for diagnosis of GCA.
Giant cell arteritis (GCA), also known as temporal or cranial arteritis, is a disease caused by inflammation of medium- and large-sized arteries.1,2 The aortic arch and its major branches (i.e., the carotid and cranial arteries) are affected most often, but other arteries throughout the body may also be involved.1,3-5
Polymyalgia rheumatica (PMR), a disease characterized by inflammation of the lining of joints, is frequently associated with GCA.5,6 It has been suggested that GCA and PMR are different manifestations of the same disease.5,7 While GCA mainly effects the cranial arteries and causes headaches, PMR causes sore and stiff muscles of the neck, pelvic girdle, and shoulders.5,6 These two disease states are often seen simultaneously. PMR has been found to be present in 40% to 60% of GCA patients; 10% to 20% of PMR patients will eventually develop GCA.1,6,8 The cause of each condition remains unknown, but both mainly occur in patients older than age 50 years.1 The onset of symptoms may be sudden or gradual. In individuals with PMR, the stiffness is worse in the morning and after periods of inactivity and usually lasts longer than 30 minutes.1,5
Many of the same laboratory tests can be performed in the pursuit of diagnosis, but persons with GCA and/or PMR may have normal erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP).6 Anemia, malaise, weight loss, and fever are some of the most common side effects of both disease states.6,8 Biopsy of the artery or muscle is required to confirm a diagnosis of GCA and PMR, respectively.
PMR can be debilitating, but normal daily function can be regained with treatment.6 Corticosteroid therapy is the mainstay treatment of GCA and PMR. With PMR, a 10- to 20-mg dose of prednisone is needed; a much higher dose is usually required to treat GCA.6 If either condition is left untreated, major complications can occur (e.g., vision loss with GCA and disability with PMR).8
GCA is a disease that primarily affects individuals aged 50 years and older, but the average age of diagnosis is 72 years.4 As the population ages, so does the prevalence of GCA, which could be attributable to increased provider awareness.2,5 The overall incidence of GCA in individuals older than age 50 years is 15-25 per 100,000 per year; this increases to 44.7 per 100,000 per year in individuals older than age 90 years.3
GCA affects women two to four times more often than men.1,3,7 Those of northern European descent, particularly Scandinavian populations, have a higher incidence GCA. The incidence is much lower in Asian, Hispanic, and black individuals.2
While the cause of GCA is unknown, a combination of environmental and genetic factors has been suggested as a likely influence on prevalence and severity.1,5,8 From a genetic standpoint, preferences have been discovered in several of the HLA heplocytes.1,4 Research has found a genetic predisposition to the HLA-DR4 allele, and other genetic associations have been seen with HLA-DRB1 and HLA-DRB1*04 variants.1,5,9 It is thought that these alleles—or the amount of the internal elastic lamina within vessels—may determine the severity of the disease.5,7
The process through which GCA forms remains unknown, but experimental studies have shown that GCA is likely an antigen-driven disease.1,5,8 It is theorized that dendritic cells within the tunica adventitia or tunica media vasorum initiate the disease by activating the CD4+ T-cells and synchronize macrophage differentiation.1,5,8 The recruited T-cells then undergo clonal expansion and produce mainly IL-2 and IFN-gamma cytokines; the IFN-gamma cytokines are thought to be involved with overt arteritis.1,5 These inflammatory mediators cause fragmentation of the elastic lamina, thereby triggering the repair process, which then initiates intimal hyperplasia leading to occlusion of the vessel followed by ischemia.3,5 The prevalence of GCA in the cranial arteries is believed to be attributable to the fact that as these vessels penetrate the dura, they become thinner and have much less elastic lamina and no vasa vasorum.5