Giant Cell Arteritis
What Is It, Causes, Diagnosis, and More
Authors: Maria Giulia Boemi, Kelsey LaFayette, DNP
Editors: Alyssa Haag, Lily Guo, Jessica Reynolds, MS
Copyeditor: David G. Walker
What is giant cell arteritis?
Giant cell arteritis (GCA), also called temporal arteritis, cranial arteritis, and Horton disease, is a type of vasculitis, or disorder that causes inflammation of blood vessels. It is characterized by granulomatous inflammation (i.e., a collection of macrophages that are usually accompanied by helper T-cells) within artery walls that typically affects the medium and large arteries of the head and neck, like the temporal arteries. It may also affect other arteries, including the aorta, subclavian, iliac, ophthalmic, occipital, and vertebral arteries. Prompt diagnosis and treatment of giant cell arteritis is important to avoid serious complications, like permanent vision loss.
What causes giant cell arteritis?
The cause of giant cell arteritis is currently unknown; however, several genetic and environmental factors have been suspected. Since GCA typically only occurs in adults who are 50 years or older, advancing age is a known risk factor. Other risk factors include Scandinavian ancestry and tobacco smoking. Those assigned female at birth are also more likely to be affected by GCA.The pathogenesis of GCA is thought to be due to an inappropriate response to endothelial injury leading to immune system dysregulation and inflammation. In response to endothelial injury, CD4+ T-cells become activated and induce macrophage differentiation, T-cell production of interferon-gamma, and development of granulomatous inflammation within arterial walls. “Giant cell” formation may also occur as activated macrophages fuse together. These inflammatory changes can result in narrowing of the arterial lumen, arterial wall proliferation and disruption, and thrombotic changes. Ultimately, poor blood flow through affected arteries and tissue ischemia can result.
What are the signs and symptoms of giant cell arteritis?
The signs and symptoms of giant cell arteritis can vary depending on which arteries are affected. Most individuals present with one or more constitutional symptoms, such as fever, fatigue, weight loss, and malaise. The temporal artery is most commonly affected; therefore, many individuals also present with temporal headaches. Nonetheless, headaches may be generalized, occipital, or periorbital. A specific symptom of GCA is jaw claudication, or pain while chewing and talking, which indicates poor blood flow to the jaw muscles due to inflammation. Sudden transient unilateral or bilateral vision loss (i.e., amaurosis fugax) can occur if there is involvement of the ophthalmic arteries. Individuals may also experience transient ischemia of the brain, specifically in the posterior circulation, leading to stroke-like symptoms of imbalance, vertigo, and unilateral limb weakness. Involvement of the aorta can cause aortitis or the development of aneurysms, which carry the risk of rupture or dissection. Other signs and symptoms of giant cell arteritis are usually due to stenosis or ischemia in various parts of the body and may include peripheral neuropathy, cough, sore throat, bruit, asymmetrical upper extremity pulses, and upper extremity pain.Giant cell arteritis is also associated with polymyalgia rheumatica, an autoimmune disorder that causes muscle inflammation. Polymyalgia rheumatica may occur before, during, or after a giant cell arteritis diagnosis. Therefore, the signs and symptoms of polymyalgia rheumatica (e.g., pain, stiffness, and decreased range of motion of the shoulders and hips) can also be present with GCA.
How is giant cell arteritis diagnosed?
The diagnosis of giant cell arteritis first relies on history, clinical presentation, and blood tests before confirmation with a tissue sample. GCA may be suspected in an adult with a history of polymyalgia rheumatica or new-onset headache. Pain, tenderness, or nodularity upon palpation of the temporal artery may be discovered on physical examination and is specific for GCA. Individuals with GCA may have anemia (i.e., low hemoglobin or hematocrit) on a CBC blood test. Inflammatory markers, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), may be often elevated. However, ESR is a non-specific marker for inflammation and may therefore be normal in individuals with GCA. On the other hand, CRP is a more sensitive marker for inflammation in GCA and is usually elevated. Levels of serum interleukin-6 (IL-6) are also commonly elevated. Autoantibodies, such as rheumatoid factors, antinuclear antibodies (ANA), and antineutrophil cytoplasmic antibodies (ANCAs) are typically negative in GCA. When clinical suspicion for GCA is high, a biopsy of the temporal artery or other affected artery is considered the gold standard diagnostic test and should be performed as early as possible to yield an accurate diagnosis. If biopsy is negative and high clinical suspicion remains or extracranial artery involvement is suspected, then vascular imaging with Doppler ultrasound, CT, or MRI may be useful for diagnosis.
How is giant cell arteritis treated?
The mainstay of treatment for all cases of giant cell arteritis is corticosteroids (e.g., prednisone). When GCA is suspected, it is imperative to initiate high-dose corticosteroids as soon as possible, even before diagnosis is confirmed with biopsy to prevent further progression of GCA and irreversible damage. High-dose steroids are continued for several weeks before a gradual taper over the course of months. Most individuals require more than one year of steroid treatment and some may need long-term treatment with daily low-dose corticosteroids. Tocilizumab, a monoclonal antibody inhibiting IL-6, is also approved to treat GCA and may be used as an alternative treatment to steroids. Individuals should be carefully monitored during the course of treatment for relapses, normalization of CRP levels, and medication side effects (e.g., osteoporosis, hyperglycemia, adrenal insufficiency).
What are the most important facts to know about giant cell arteritis?
Giant cell arteritis, also called temporal arteritis, is the most common type of vasculitis characterized by granulomatous inflammation within arterial walls that most commonly affects the temporal arteries. The cause of GCA is currently undetermined. Risk factors for GCA include age of 50 years or older, tobacco use, and Scandinavian ancestry. Common signs and symptoms of giant cell arteritis include constitutional symptoms (e.g., fever and fatigue); temporal headaches, loss of vision, jaw claudication, nodularity or tenderness of the temporal artery, and muscle pain and stiffness. GCA is suspected based on clinical presentation and lab studies, which may indicate low hemoglobin or hematocrit, elevated ESR, and elevated CRP. The diagnosis is confirmed with a biopsy of the temporal artery performed as soon as possible. Treatment of giant cell arteritis consists of early administration of high-dose corticosteroids to avoid disease progression and permanent blindness. Toclizumab was also recently approved as an alternative treatment for giant cell arteritis.
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