Giant cell arteritis (known as GCA or temporal arteritis) is an autoimmune condition that typically affects those over the age of 50, typically causing inflammation of arteries (referred to as vasculitis) with a predilection for the temporal arteries and its branches. The immune system, which normally protects the body from infections, begins to turn against the body's own healthy tissues, causing symptoms such as headaches, tenderness of the temples and scalp, jaw and tongue discomfort when chewing, and visual disturbance. Giant cell arteritis often co-exists with a condition called polymyalgia rheumatica.

Due to its capability of causing visual impairment, giant cell arteritis is considered a medical emergency. When giant cell arteritis is suspected, prompt medical attention and treatment is necessary.

The diagnosis of giant cell arteritis is made through a physical assessment in combination with some, or all, of the following investigations to look for evidence of inflammation: blood tests, temporal artery ultrasound scan, temporal artery biopsy and PET-CT scan (a type of scan that uses a specific radioactive tracer).

Treatment with steroids should be initiated promptly to avoid complications such as visual loss. The dose of steroid is tailored according to the presence of visual symptoms, or other factors predictive of impending visual symptoms, with a symptomatic response usually observed within one to two weeks. Steroid treatment may be required for up to two or three years, although initiation of steroid-sparing disease modifying anti-rheumatic drugs (DMARDs) can improve treatment success rates.