Giant cell arteritis (GCA) is a common inflammation disease of medium- to large-sized arteries. These arteries can become narrowed, restricting blood flow to affected parts of the body. Arteries in the head are the most commonly affected, but arteries in the chest, neck, heart, and other parts of the body may also be involved.
When the arteries in the temples of the head are affected, it is termed temporal arteritis or cranial arteritis. Giant cells are immune cells found in high concentrations inside affected arteries.
There are three patterns seen in giant cell arteritis: primarily affecting the head, primarily affecting the larger vessels of the chest and neck, and a wasting, generalized disease.
GCA is unusual in people under 50 years of age. Among those over 50, it strikes as many as 1 in 500 people in the United States. Two-thirds of people who have giant cell arteritis are women. People of African descent are less commonly affected.
GCA is closely associated with a disease called polymyalgia rheumatica (PMR), which many experts believe is a different manifestation of the same underlying disorder. 10% to 20% of people with PMR develop GCA. More than 50% of people with GCA also have symptoms of PMR.
Arteritis may appear before, during, or after the onset of PMR. The primary symptoms of PMR are severe stiffness and pain in the neck, shoulder, and hip muscles. There may also be fatigue, joint pain, and anemia. Fortunately, the same treatment is effective for both conditions, but GCA requires much higher doses.
GCA is an autoimmune disease in which the body's immune system mistakenly attacks the person's own tissue. Autoimmune diseases in general are poorly understood. They tend to run in families, but not so much that we can say they're inherited or genetic diseases. Many doctors believe it takes a combination of predisposing genes and environmental factors to trigger the condition.