It is an auto-immune condition that happens because of a faulty immune system reaction, when the immune system attacks healthy cells by mistake.
It is now called giant cell arteritis (GCA) because research has shown that it can affect not only the temporal arteries. Other blood vessels that can develop GCA include the thoracic aorta and its branches, in the head and neck.
The term "giant cell" is used because biopsies of inflamed temporal arteries, seen under a microscope, show enlarged cells.
GCA has been known since at least the 10th century. Other names include cranial arteritis and Horton disease.
GCA is most common after the age of 50 years. The chances of developing it increase with age. It affects around 18 people in every 100,00 each year, and it is most likely to occur when a person is in their 80s.
It is two or three times more likely to affect women than men.
A persistent headache and visual disturbances can be symptoms of temporal arteritis.
The main symptom is a severe, persistent, and possibly throbbing headache, usually on the side or at the front of the head.
Two in every three people with this condition will have a headache.
Further symptoms include:
- tender temples
- mouth-related pain, especially affecting the jaw, that may be felt when eating
- pain in the tongue, throat, or face
- pain or swelling on top of the head, or scalp
- blurry or double vision
Anyone who experiences these symptoms should see a doctor for diagnosis and treatment. If vision problems occur, immediate medical help is needed.
The most serious possible complication is loss of vision, which can occur suddenly and be permanent.
It can happen if the vasculitis affects an artery that supplies an eye, causing damage to the optic nerve.
Signs of visual disturbances include:
- blurred or double vision
- blind spots
- drooping eyelid
Brief periods of total vision loss in one eye may be followed by total and permanent vision loss.
Vision loss affects between 14 and 20 percent of people with GCA. Before the introduction of corticosteroids, the rate was 30 to 60 percent.
If treatment for GCA is started before any effect on vision, the risk of blindness happening later is reduced to 1 percent or lower.
- Fifty-eight percent experience visual improvements if treatment is started within 24 hours
- Six percent experience improvements if treatment starts "after a delay."
It is also important to monitor and maintain vision in the unaffected eye.
Visual loss affects the other eye within days to weeks in 50 percent of people with a diagnosis of GCA.
It is important to see a doctor with any symptoms that could indicate GCA.
A doctor will consider the symptoms the patient describes, ask questions, and explore other possibilities. They will also do a physical examination.
If GCA is a possibility, treatment should start right away.
Tests that may be used to diagnose this condition include:
- blood tests to assess for erythrocyte sedimentation rate
- ultrasound to check for abnormalities in the temporal arteries
- a biopsy of the artery wall, carried out under local anesthetic, to assess for inflammation of the artery
Treatment may begin before the results of a biopsy, because of the risk of vision loss.
GCA affects the arteries that supply the head and the brain with blood.
GCA affects the temporal arteries and it can develop in the thoracic artery, too.
There is one temporal artery on each side of the head.
Each one runs over the part of the skull that is above and around the ear. The two arteries themselves run up in front of the ear. They branch off from the two main blood supplies to the head from the heart.
The exact cause of GCA is unknown, but it is thought to be an auto-immune condition, in which the body's immune system attacks healthy cells in the arteries. This leads to inflammation.
When the blood vessel lining becomes inflamed, giant cell lesions can form.
These giant cells form when numerous immune cells fuse together. These immune cells are a type of white blood cell.
Giant cells also play a role in tuberculosis (TB), leprosy, some fungal infections, and other conditions.
Risk factors include ethnicity, being aged over 50 years, having another health condition.
Why some people develop temporal arteritis is not fully understood. It is also unclear why some groups are more at risk than others.
Age is a risk factor. The average age at which GCA starts is 70 years.
Other possible factors may include:
- geographical location
- seasonal factors
- genetic factors
- exposure to viruses or toxins
- having other health conditions related to vasculitis or inflammation
GCA and polymyalgia rheumatica
Polymyalgia rheumatica (PMR) is a form of inflammation that affects the whole body. Symptoms include aching and stiffness, especially in the neck, shoulders, upper arms, and around the pelvis.
Like GCA, it is also more common in people aged over 55 years and affects more women than men.
GCA and systemic vasculitis
Systemic vasculitis is related to temporal arteritis because the inflammation of cranial arteries is one form of vasculitis.
Systemic vasculitis refers to a range of disorders that involve inflammation and damage to blood vessel walls that can lead to tissue death.
The different types are classified and managed according to the blood vessel size affected — large, medium, or small — and the area of effect, such as on an organ.
With temporal arteritis, the arteries affected are medium, and the eye is at risk.
The treatment approach for both systemic vasculitis and GCA is with glucocorticosteroids.
Why is temporal arteritis more common in Minnesota?
People with a northern European background show a higher risk of developing temporal arteritis. The exact reason is not clear.
One study into rates of temporal arteritis in the United States looked at where the population is largely made up of that ethnic background: Minnesota.
Studying Olmsted County in particular, the researchers found that the rate here was as high as in Sweden, a country with one of the highest rates of temporal arteritis.
Over a 50-year period, the study found that there were almost 20 cases for every 100,000 in people across that time. In the Mediterranean region, the number of cases is low. In northern Italy, where temporal arteritis is at its lowest, there are 6.9 cases for every 100,000 people.
The authors wrote that the north-south divide could be due to environmental, genetic or ethnic factors.
However, average rates of temporal arteritis in the population overall are relatively low, although they are more common in older people.
Treatment will normally start at once, possibly before biopsy results are confirmed, to reduce the risk of complications. The person may need to see a specialist doctor.
High-dose corticosteroid drugs have been the standard treatment since the 1950s, but recently, another drug was approved: Actemra.
These prevent complications such as loss of vision. The recommendation is to initiate them "immediately and aggressively."
The dose is usually 40 to 60 milligram (mg) of prednisone (such as Orasone or Deltasone) each day for around a month. Symptoms should improve rapidly after treatment begins.
People who experience visual symptoms will have the higher dose.
After a month, the dose decreases gradually. Eventually, a person may take 5 to 10 mg daily for several months.
Treatment must start quickly to prevent deterioration of vision.
Over half of all people who receive corticosteroids for GCA will experience adverse effects.
In 2017, another drug, Actemra (tocilizumab), received approval from the Food and Drug Administration (FDA) to treat this condition.
It is given as an injection. Actemra is an interleukin-6 (IL-6) receptor antagonist that is also used to treat rheumatoid arthritis. It affects the immune system.
Side effects include:
- stomach tears
- changes in blood composition
- a higher risk of some cancers
- possible allergic reactions
- nervous system complications
Anyone who experiences the following after using this drug should see their doctor:
- upper respiratory tract infections
- high blood pressure
- a reaction at the injection site
A doctor may prescribe aspirin to help prevent blood clots, unless the person has another condition that does not allow this, such as a stomach ulcer or bleeding disorder.
Without treatment, the outlook is poor, but with modern medicine, symptoms of GCA usually improve within days of starting treatment, and vision loss is now rare.
However, the time needed for a full recovery can vary widely. The average length of treatment is 2 years, but for some people, treatment will continue for 5 years or longer.
People who have GCA also have a higher chance of having an aortic aneurysm and cardiovascular disease.
In addition, long-term steroid use can lead to some health problems.
Studies do not suggest that a person with GCA has a higher risk of dying earlier than a person without the condition. However, it is important to attend all follow-up appointments to ensure that any complications receive treatment in good time.