GCA is a rare autoimmune disorder and is the most common type of inflammation of medium- to large-sized blood vessels in the body. It usually only occurs in older adults. The most common symptoms of GCA include headache, pain in the shoulders and hips (polymyalgia rheumatica), pain in the jaw (jaw claudication), fever, and blurred vision. Organ-specific markers of injury or damage as well as direct markers of vascular damage and inflammation are currently used by clinicians to assess GCA disease progression; however, these markers are not very useful in guiding treatment. There are also blood tests that clinicians use to monitor GCA activity, such as erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), but these tests lack specificity and sensitivity. Most treatments available now for GCA are toxic, therefore if other markers indicating disease activity can be found, it may lead to the development of less toxic treatments. This study will use new scientific methods to identify new biomarkers that can be used to monitor disease activity in GCA patients. These biomarkers may be used to help direct clinical care for GCA patients and assist in future drug development.

This study will last 5 years. Study visits will occur monthly for the first year, then every 3 months thereafter for the remainder of the study. Blood and urine collection will occur at every visit. A physical exam and medical and medication history will occur every 3 months; also, participants will be asked to complete several questionnaires to assess disease activity, health status, and tobacco, alcohol, and drug use. Participants may have additional study visits if a disease flare or disease-releated complications occur during the study.

Adults with giant cell arteritis. Enrollment will be sequential and participants will have disease in various stages and of different duration.

Inclusion Criteria:

• Diagnosis of GCA, meeting at least 3 of the following 5 American College of Rheumatology (ACR) criteria for the diagnosis of GCA:

  1. At least 50 years of age at disease onset
  2. New onset or new type of localized pain in the head
  3. Temporal artery abnormality (i.e., temporal artery tenderness to palpation or decreased pulsation unrelated to ateriosclerosis of cervical arteries)
  4. ESR of greater than 40 mm in the first hour by the Westergren method
  5. Temporal artery biopsy showing vasculitis characterized by a predominance of mononuclear cell infiltration or granulomatous inflammation, usually with multinucleated giant cells

Exclusion Criteria:

• Unable to give informed consent and sign the conset form