Giant cell arteritis: Suspect it, treat it promptly
ABSTRACTGiant cell arteritis is the most common form of vasculitis affecting older people, and the diagnosis should be considered in older patients who present with the new onset of headache, visual dysfunction, polymyalgia rheumatica, or systemic inflammatory symptoms. Physicians should be familiar with its variety of clinical presentations and the abnormal laboratory findings associated with it.
KEY POINTS
- Giant cell arteritis is often associated with an intense acute-phase response and cranial symptoms.
- Large-vessel involvement is commonly present and may result in serious complications such as visual loss, stroke, limb claudication, and aortic aneurysm.
- The diagnosis is usually confirmed by an abnormal temporal artery biopsy.
- Symptoms of giant cell arteritis usually respond rapidly and completely to glucocorticoid therapy, still the mainstay of treatment. Most patients need prolonged therapy.
- Several studies have evaluated alternative drugs in an attempt to avoid toxicity from long-term use of glucocorticoids. Results have been mixed, and further study is needed.
CONSIDER THE DIAGNOSIS IN OLDER PATIENTS
Giant cell arteritis should always be considered in patients over age 50 who have any of the clinical features described above. It is therefore very important to be familiar with its symptoms and signs.
A complete and detailed history and a detailed but focused physical examination that includes a comprehensive vascular examination are the first and most important steps in establishing the diagnosis. The vascular examination includes measuring the blood pressure in all four extremities, palpating the peripheral pulses, listening for bruits, and palpating the temporal arteries.
Temporal artery biopsy: The gold standard
Confirming the diagnosis of giant cell arteritis requires histologic findings of inflammation in the temporal artery. Superficial temporal artery biopsy is recommended for diagnostic confirmation in patients who have cranial symptoms and other signs suggesting the disease.
The biopsy should be performed on the same side as the symptoms or abnormal findings on examination. Performing a biopsy in both temporal arteries may increase the diagnostic yield but may not need to be done routinely.13
Although some experts recommend temporal artery biopsy in all patients in whom giant cell arteritis is suspected, biopsy has a lower diagnostic yield in patients who have no cranial symptoms. Interestingly, 5% to 15% of temporal artery biopsies performed in patients who had isolated polymyalgia rheumatica were found to be positive.14,15 Patients with polymyalgia rheumatica and no clinical symptoms to suggest giant cell arteritis generally are not biopsied.
The segmental nature of the inflammation involving the temporal artery in giant cell arteritis may result in negative biopsy results in patients with giant cell arteritis. A temporal artery biopsy length of 5 mm or less has a very low (8%) rate of positive results, whereas a length longer than 20 mm exceeds a 50% rate of positive results. Although the optimal length of a temporal artery specimen is still debated, a longer biopsy specimen should be obtained to increase the chance of arterial specimens showing inflammatory changes.16,17
Laboratory studies: Acute-phase reactants may be elevated
High levels of acute-phase reactants should increase one’s suspicion of giant cell arteritis. Elevations in the erythrocyte sedimentation rate and C-reactive protein and interleukin 6 levels reflect the inflammatory process in this disease.19 However, not all patients with giant cell arteritis have a high sedimentation rate, and as many as 20% of patients with biopsy-proven giant cell arteritis have a normal sedimentation rate before therapy.20 Therefore, a normal sedimentation rate does not exclude the diagnosis of giant cell arteritis and should not delay its diagnosis and treatment.
As a result of systemic inflammation, the patient may also present with normochromic normocytic anemia, leukocytosis, and thrombocytosis.
Imaging studies are controversial
Imaging studies are potentially useful diagnostic tools in large-vessel vasculitis but are still the subject of significant controversy.
Ultrasonography of the temporal artery has been a controversial subject in many studies.21,22 Color duplex ultrasonography of the temporal artery has been reported to be helpful in the diagnosis of giant cell arteritis (showing a “halo” around the arterial lumen), but further studies are needed to establish its clinical utility.
At this time, temporal artery biopsy remains the gold standard diagnostic test for giant cell arteritis, and ultrasonography is neither a substitute for biopsy nor a screening test for this disease.23 Some have suggested, however, that ultrasonography may help to identify the best site for biopsy of the temporal artery in some patients.
Arteriography is an accurate technique for evaluating the vessel lumen and allows for measuring central blood pressure and performing vascular interventions. However, because of potential complications, it has been largely replaced by noninvasive angiographic imaging to delineate vascular anatomy.
