Giant Cell Arteritis (GCA), also known as temporal arteritis, is a chronic granulomatous pan-arteritis occurring in the elderly. The etiology remains unclear. It commonly involves the aortic arch and its primary branches, especially the temporal artery. Typical manifestations include temporal headache, scalp tenderness, intermittent jaw claudication, and visual disturbances. This condition exclusively affects individuals over the age of 50, with a peak onset age of 74 years. The incidence ranges from 1.4 to 27.3 per 100,000 people, with significant regional differences in prevalence. It is the most common vasculitis in elderly individuals in Western countries, with the highest prevalence recorded in Northern Europe and the lowest in Asia. Women are 2–4 times more likely to develop this condition than men.
Etiology
The cause of GCA is not well understood, but it is associated with genetic factors (e.g., HLA-DRB101 and HLA-DRB104 haplotypes), advanced age, degenerative changes in blood vessels, and external factors such as smoking and viral infections.
Pathology
The pathological changes in GCA are almost identical to those in Takayasu arteritis, characterized as granulomatous arteritis involving the entire arterial wall. Inflammatory cell infiltration occurs throughout the arterial wall and is often accompanied by intimal hyperplasia and disruption of the internal elastic lamina. Granulomatous lesions with giant cells may be present. As the disease progresses, collagen deposition, fibrosis, wall thickening, and lumen narrowing may develop, sometimes leading to secondary thrombus formation.
Clinical Manifestations
The onset is often insidious. Patients may experience symptoms such as fever, general malaise, fatigue, joint and muscle pain, poor appetite, and weight loss. About 70% of patients present with unilateral or bilateral temporal headache, scalp tenderness, and intermittent jaw claudication. The temporal superficial artery may appear thickened, hardened, nodular, and tender. Other arteries, such as the occipital, facial, and posterior auricular arteries, may also be involved.
Around 30% of patients exhibit ischemic symptoms in the head and neck arteries, including vision impairment, diplopia, ophthalmoplegia, and even blindness. Hearing loss and dizziness are also common. In 15% of cases, ischemic symptoms involving the aortic arch and its branches may appear, such as intermittent claudication, numbness, weakness, diminished or absent pulses, reduced or undetectable blood pressure, or unequal blood pressure between the two upper limbs.
Additionally, 40–60% of patients have concurrent polymyalgia rheumatica, characterized by pain and morning stiffness in the neck, shoulder girdle, and pelvic girdle muscles, though overt muscle tenderness and weakness are generally not evident.
Laboratory Tests
Common laboratory findings include anemia, elevated leukocyte and platelet counts, and significantly increased erythrocyte sedimentation rate (ESR), which is often higher than 50 mm/h. Elevated C-reactive protein (CRP) levels are also observed and represent a hallmark abnormality in GCA.
Diagnosis
A diagnosis of GCA can be established in individuals older than 50 years who develop new unilateral or bilateral temporal headaches, diminished or absent temporal artery pulsation, or thickened and hardened temporal arteries. A biopsy showing granulomatous arteritis is diagnostic. However, due to the segmental nature of temporal artery involvement, biopsies may yield false-negative results. In such cases, imaging methods, including temporal artery angiography, CTA, magnetic resonance imaging (MRI) of the temporal artery, and PET, can help identify temporal artery lesions and contribute to the diagnosis.
Treatment and Prognosis
GCA responds exceptionally well to glucocorticoid therapy. Prednisone at a dose of 40–60 mg/day often leads to symptom resolution within one week. However, relapse is common after dose reduction, necessitating long-term maintenance at a low dose. For patients who experience disease relapse during the slow tapering of glucocorticoids, immunosuppressants such as methotrexate, azathioprine, or cyclophosphamide (CTX) may be added to the treatment regimen.
In cases with vision changes, especially those with sudden vision deterioration, pulse therapy using 500–1,000 mg/day of methylprednisolone for three days should be considered. IL-6 receptor monoclonal antibodies have been shown to be particularly effective in treating GCA and can reduce the required glucocorticoid dosage. They have become a first-line treatment option for this condition.
The prognosis for most patients is favorable.