Giant Cell Arteritis · What Is It, Causes, Diagnosis, and More

The cause of GCA 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. Biological females are also more likely to be affected by GCA.   

The pathogenesis of GCA is thought to involve 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 may result in tissue ischemia. 

The signs and GCA 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. Because the temporal artery is mostly affected, many individuals also present with temporal headaches; however, the headaches may also 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 the ophthalmic arteries are involved. Permanent vision loss, although not so common, is the most severe complication of GCA. 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 of  GCA 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.  

GCA is also associated with polymyalgia rheumatica, an autoimmune disorder that causes muscle inflammation. Polymyalgia rheumatica may occur before, during, or after a GCA 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.