Diagnosis

The diagnosis of PMR/GCA is based upon typical clinical signs and symptoms, including shoulder and hip girdle aching and an elevated sedimentation rate in patients older than 50 years, and in GCA, new onset of localized headache with temporal artery tenderness, positive ESR, and an abnormal temporal artery biopsy.

GCA occasionally can occur with a low sedimentation rate. In a population-based study of 167 patients diagnosed between 1950 and 1998, 11% had an ESR of less than 50 mm in the first hour, and nine (5%) had ESRs of less than 40 mm per hour (17). These patients were less likely to have constitutional symptoms than patients with elevated ESRs. However, a review of 941 patients with biopsy-proven GCA found that only 4% had a normal ESR, underlining the sensitivity of an elevated sedimentation rate in the initial diagnosis of this condition (18).

A temporal artery biopsy should be performed in all patients in whom a diagnosis of GCA is suspected (19). Biopsies reveal medial and intimal inflammation and disruption of the internal elastic lamina. Lymphocytic and macrocytic infiltrates are typical, causing disruption of the arterial wall (Fig. 4). Multinucleated giant cells are frequently but not invariably present. Luminal occlusion and ischemia may result. The sensitivity of a temporal artery biopsy is 58% for diagnosis of GCA (20). A negative temporal artery biopsy has a high negative predictive value, 90%, so that if the temporal artery biopsy is negative, the patient may have GCA, but the probability is low (20). The predicting characteristics with which a

FIGURE 4 Photomicrographs of active arteritis in a temporal artery biopsy. (A) Transmural inflammation with marked intimal thickening (hematoxylin-eosin, 40X). (B) Elastic stain highlighting disruption of the IEL; arrows indicate a small segment of intact IEL (Verhoeff van Gieson, 40X). (C) Higher power view showing proliferation of intimal fibroblasts and transmural inflammation with multinucleated giant cells present at the media-intima junction (hematoxylin-eosin, 200X). (D) Elastic stain showing giant cells and complete loss of the IEL (Verhoeff van Gieson, 200X). Abbreviations: GCA, giant cell arteritis; IEL, internal elastic lamina. Source: Courtesy of Dylan Miller, MD, Mayo Clinic, Rochester, MN, U.S.A.

FIGURE 4 Photomicrographs of active arteritis in a temporal artery biopsy. (A) Transmural inflammation with marked intimal thickening (hematoxylin-eosin, 40X). (B) Elastic stain highlighting disruption of the IEL; arrows indicate a small segment of intact IEL (Verhoeff van Gieson, 40X). (C) Higher power view showing proliferation of intimal fibroblasts and transmural inflammation with multinucleated giant cells present at the media-intima junction (hematoxylin-eosin, 200X). (D) Elastic stain showing giant cells and complete loss of the IEL (Verhoeff van Gieson, 200X). Abbreviations: GCA, giant cell arteritis; IEL, internal elastic lamina. Source: Courtesy of Dylan Miller, MD, Mayo Clinic, Rochester, MN, U.S.A.

positive biopsy is associated are new headache, jaw claudication, abnormal temporal artery on examination, and high sedimentation rate and platelet count (21). Of patients who are suspected of having GCA and have no claudications and normal temporal arteries but who have synovitis, 95% are biopsy negative (21).

When performing a temporal artery biopsy, in general, a frozen section from the first side should be evaluated and if reported negative, and there is high suspicion of GCA, a second biopsy from the opposite side should be obtained. Prednisone therapy prior to biopsy may interfere with the results of the biopsy; however, 28% of patients who have received more than 14 days of standard treatment for GCA will have a positive biopsy, whereas, 31% of untreated patients had an initial positive biopsy in one series (22).

Vascular imaging techniques can be very helpful in evaluating patients with GCA. Particularly, conventional and MRI angiography may be helpful in visualizing typical abnormalities of the large- and medium-sized arteries and their walls, and stenotic narrowing, aneurysmal dilatation, particularly of the aortic root, ascending and/or descending aorta, may be seen (2,3). Ultrasonography has been advocated as a means of detecting evidence of inflammation in the temporal artery, and although attractive as a noninvasive and inexpensive method, the sensitivity and specificity have not been adequately established. Positron emission tomography may ultimately be found helpful in assessing disease activity. It has been suggested that it may have a sensitivity of 56% and a specificity of 98% in differentiating GCA from PMR (23).

The differential diagnosis of GCA includes other systemic inflammatory vasculitides, particularly polyarteritis nodosa and Wegener's granulomatosis (Chapter 8). Takayasu's arteritis typically is a GCA of patients less than 40 years of age. Subacute bacterial endocarditis, organ cancers, and systemic amyloidosis may also masquerade as GCA. Rheumatoid arthritis (RA) (the elderly onset RA), spondyloarthritis, and fibromyalgia, as well as solid organ cancers and other malignancies, may cause symptoms of PMR.

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