Both giant-cell arteritis and polymyalgia rheumatica are immune-mediated diseases that are treated with glucocorticoids, with higher doses used for giant-cell arteritis. In our latest Clinical Practice article, prompt initiation of high doses and a biopsy are recommended when ischemic optic neuropathy is suspected.
Giant-cell arteritis is an inflammatory vasculopathy that typically occurs in medium and large arteries with well-developed wall layers and adventitial vasa vasorum. The vascular beds that are usually affected include the external carotid branches (e.g., temporal and occipital arteries), the ophthalmic, vertebral, distal subclavian, and axillary arteries, and the thoracic aorta. Polymyalgia rheumatica causes aching and stiffness in selected muscle groups, predominantly in the neck, shoulders, upper arms, and pelvic girdle. Symptoms are most pronounced in the morning.
• What is the epidemiology of giant-cell arteritis and polymyalgia rheumatica, and how often do the diagnoses overlap?
Giant-cell arteritis and polymyalgia rheumatica have multiple risk factors and pathogenic abnormalities in common. Approximately 50% of patients with giant-cell arteritis present with polymyalgia rheumatica before, at the time of, or after the diagnosis of vasculitis. Symptoms of polymyalgia rheumatica often appear when the therapy for giant-cell arteritis is being tapered. Both giant-cell arteritis and polymyalgia rheumatica are diseases that affect the elderly, with a peak incidence at the age of 70 to 80 years; age (50 years or older) is considered a criterion for the diagnosis. Women account for 65 to 75% of patients. Polymyalgia rheumatica occurs at a frequency that is 3 to 10 times that of giant-cell arteritis.
• What are laboratory results in patients with giant-cell arteritis and polymyalgia rheumatica?
Marked elevations in the erythrocyte sedimentation rate (ESR) and the level of C-reactive protein (CRP) are common in giant-cell arteritis and polymyalgia rheumatica, as are the presence of thrombocytosis and anemia. In a cohort of 764 patients with suspected giant-cell arteritis who underwent biopsy, with the diagnosis confirmed in 177 patients, the sensitivity of an elevated ESR was 84% and that of an elevated CRP level was 86%; the specificity of these markers was low, however, at 30%. Only 4% of patients with confirmed giant-cell arteritis had both a normal ESR and a normal CRP level at the time of diagnosis. Assessment of inflammatory markers is helpful during diagnostic evaluation and long-term monitoring, but elevated levels of these markers should not be the only indication for immunosuppressive therapy. No highly specific biomarkers for giant-cell arteritis and polymyalgia rheumatica have been validated.
Morning Report Questions
Q: What is the standard for diagnosis of suspected giant-cell arteritis?
A: In cases of suspected giant-cell arteritis, histologic verification of vasculitis should be sought by means of a temporal-artery biopsy with assessment of a vascular segment that is 1.5 to 2.0 cm in length. Histologic analysis is the standard for diagnosis; it can detect small inflammatory infiltrates and can also distinguish giant-cell arteritis from non-giant-cell arteritis arteritides (e.g., ANCA-associated vasculitis). High-field-strength MRI may emerge as a method that is sensitive to the detection of temporal-artery inflammation, but neither ultrasonography nor MRI has yet replaced temporal-artery biopsy, which is highly sensitive for even minor inflammatory changes.
Q: What is the optimal treatment for giant-cell arteritis and polymyalgia rheumatica?
A: Giant-cell arteritis and polymyalgia rheumatica are responsive to glucocorticoids. Most treatment recommendations are based on clinical experience rather than the results of randomized, controlled trials. Therapy for giant-cell arteritis is initiated with prednisone at a dose of 1 mg per kilogram of body weight per day. Given the risk of irreversible ischemic complications, new-onset clinical manifestations of disease indicating an unstable supply of blood to the eyes or the central nervous system (e.g., arteritic optic neuropathy) are typically managed with intravenous pulse therapy (e.g., 1000 mg of methylprednisolone per day for 3 consecutive days) to optimize immunosuppression and suppress tissue edema. The doses of glucocorticoids used to treat polymyalgia rheumatica are much lower than those used for the treatment of giant-cell arteritis. In the majority of patients, a dose of 15 to 20 mg of prednisone per day is sufficient to control myalgia. No glucocorticoid-sparing agents have been approved for the treatment of giant-cell arteritis or polymyalgia rheumatica.