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Giant Cell (Temporal) Arteritis

This is a larger- and medium-size vessel inflammatory disorder typically seen in older subjects, beyond age 50, with the peak incidence at 70-80 years of age [36]. It is most commonly seen in Caucasians of European descent [37]. An association has been reported between HLA-DR4 and HLA-DRB1 suggestive of a genetic susceptibility [38]. The female to male ratio is reported to be 3:1 [39]. There is considerable overlap with a diffuse inflammatory disorder of the muscles, polymyalgia rheumatica (PMR). Roughly 50% of patients with giant cell arteritis (GCA) develop PMR either before, during, or after the time of presentation of GCA [40]. GCA is a T-cell-mediated disorder with recruitment of both T cells and macrophages to form a granulomatous infiltrate within the affected vessels [41]. On temporal artery biopsy, one sees inflamed vascular tissue with various cytokine and other inflammatory mediators [41]. Of interest, in terms of pathogenesis, Gilden and Nagel [42] have reported a relationship between varicella zoster virus (VZV) antigen and positive GCA pathology on temporal artery biopsy. In an extension of this study [43], they found VZV antigen in 74% of 82 GCA-positive biopsies. They theorize that GCA has a viral-mediated trigger.

It is expected that the incidence of GCA will increase as the population has greater longevity, and there is a present reported incidence of 27 cases per 100,000 for those 50 years of age and older [37]. The recognition is extremely important in a timely fashion in light of the potential for ischemic optic neuritis with irreversible blindness. This is reported to affect 10-15% of patients with GCA [44]. The protection of such an occurrence with early administration of steroid therapy is utmost urgency in the clinical setting.

Manifestations

A patient presenting with new onset headache at 50 years or beyond should always raise concern about GCA. Localization to the superficial temporal artery region

Table 4.5 Features of giant cell (temporal) arteritis

1. Moderate to severe head pain in region of the superficial temporal artery

6. Elevation of the erythrocyte sedimentation rate (ESR)

2. Age > 50 years

7. Elevation of the C-reactive protein (CRP)

3. Predilection for female Caucasians

8. Systemic complaints which can include

4. Jaw claudication

fever, malaise, and weight loss

5. Neck pain

9. Temporal biopsy with characteristic granulomatous inflammation

along with tenderness to palpation of this region should heighten the degree of concern. These are the most common manifestations. There can be accompanying jaw claudication and neck pain. It is also important to recognize that there can be systemic manifestations including fever of unknown origin, lassitude, and malaise, as well as loss of appetite with weight loss. The vasculitic process can involve not only the temporal arteries but also the carotid distribution, the aortic arch, as well as the axillary, iliac, and femoral arteries [45]. There can be both arterial and venous occlusive events associated with such inflammation including both myocardial infarct and stroke [46]. Features of GCA are summarized in Table 4.5.

Diagnosis and Treatment

The American College of Rheumatology criteria [38] factors in such features as head pain in the region of the superficial temporal artery, age > 50, and elevation of the erythrocyte sedimentation rate (ESR) to > 40 mm/h to formulate their criteria for diagnosis with a reported sensitivity of 93.5% and specificity of 91.2% [45]. However, Murchison et al. [47] reported that the use of these criteria alone, without confirmatory temporal artery biopsy findings, could miss up to 25% of cases. The ESR is often quite high at 80 mm/h or above, and the C-reactive protein (CRP) is often quite elevated. These are not 100% in terms of degree of detection, however. One study of 764 subjects [48] reported a sensitivity of the ESR of 84% and the CRP of 86% but with a specificity of 30%. Overall, the yield is quite high with only 4% of patients having normal ESR and CRP values at the time of diagnosis.

Because of the low specificity for the ESR and CRP, and the need to support ongoing steroid therapy if indeed the patient has GCA, then a temporal artery biopsy is mandatory. The granulomatous inflammatory findings expected on biopsy are detected in 85-95% of GCA cases [49]. The urgency to protect against potential blindness, with steroid therapy, can lead to misdiagnosis. Saedon et al. [50] reported that clinical criteria for diagnosis, without confirmatory biopsy findings, led to immunosuppressive treatment in 61% of 112 patients which raises some concern about possible unnecessary treatment in some subjects.

A generally accepted approach is the initiation of prednisone at 1 mg per kg of body weight per day. For those patients with worrisome visual symptoms, a 3-day course of daily 1000 mg intravenous methylprednisolone would be indicated. Assuming response, various tapering courses have been implemented. It has been suggested that a reasonable approach is reduction of the dose of prednisone by 10-20% every 2 weeks down to less than 10 mg a day, and then a slower taper follows by 1 mg per month [40]. The course of tapering is obviously influenced by the ESR, and CRP results with such studies recommended monthly the first year, bimonthly the second year, and every 3-6 months for longer-term follow-up. Alternative agents for those patients either not responsive or intolerant of glucocorticoids include cyclophosphamide, methotrexate, azathioprine, and infliximab [51]. Antiviral therapy will certainly be investigated in light of the recent identification of an association with VZV [42, 43].

 
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