Giant cell arteritis

Written by Dr Badal Pal, consultant rheumatologist

What is giant cell arteritis?

Arteritis means inflammation of the arteries and it is one of those conditions in which the body's own immune system appears to 'attack' it's own tissues, in this case the lining of the arteries of the body. These are collectively called autoimmune diseases.

When examined under the microscope, the inflamed artery will be seen to contain increased numbers of a specialised type of cell of the immune system, the 'giant cell', which gives this condition it's name.

Giant cell arteritis (GCA) is considered to be a condition within the spectrum of the more general condition called polymyalgia rheumatica - of which giant cell arteritis is the more severe form of the illness. The two entities may occasionally occur together in the same patient, up to 33 per cent of patients with PMR may have evidence of GCA on temporal artery biopsy.

What causes it?

The cause of GCA is unknown. There is damage to the particular lining of the arterial wall (called 'internal elastic lamina', but other layers are also involved). This may be partly due to the ageing process, but there is probably also a genetic element that is not yet well defined.

Certain markers in blood cells called HLA antigens are found more commonly in GCA patients than the unaffected population, which is a clue to the genetic link. Highly stressful events such as a recent bereavement occasionally trigger the illness.

Abnormal immune responses occur both in blood and at cell level. Inflammation of the blood vessels is caused by the local deposition of immune complexes - protein compounds formed by the combination of antigen (the trigger to the immune system) and antibody (the immune system's response). Immune complexes have powerful effects on a range of other chemical reactions within the body, and are involved in many autoimmune diseases.

Who gets GCA and how common is it?

This varies from country to country, but in the western hemisphere, where it is common, it can affect 6-18 per 100,000 population over the age of 50. It is three times more common in women than men, and the peak age is between 60 and 75 years of age. It is very much less common in Asian people and in the Afro-Caribbean population.

What are the symptoms of GCA?

Patients notice symptoms rather suddenly and, in two thirds of cases, experience headaches (often burning or sharp, stabbing pains) that can be severe and are felt mainly over the temple area but can be at other regions, for example, at the back of the head.

Other common symptoms include:

fever

night sweats

difficulty in chewing firm food, with pain and aching in the jaws (called jaw claudication) this can affect two thirds of people.

Less common symptoms are:

visual complaints such as double vision, haziness or sudden painless loss of sight, which affects 6 to 10 per cent of people with GCA. The threat of visual loss is the most serious aspect of GCA and underlines the need to make an accurate diagnosis and treat the condition quickly and effectively.

visual loss can appear after several weeks or months of the other complaints, initially perhaps on one side but the other eye can also be affected within days. Permanent visual loss occurs in up to 20 per cent of this group of people.

tingling on the tongue and loss of taste.

patients often feel that the arteries on the temple area are swollen and painful to touch, which makes brushing of the hair often rather difficult.

The symptoms are wide ranging depending on the site where the arteries are involved. In contrast to other forms of vasculitis, GCA rarely affects the lungs, kidneys or the skin - in which case nodules on the skin and dark spots may appear.

Quite often people suffer from complaints similar to those of polymyalgia, which include:

abrupt aching and stiffness across the neck and shoulders, upper arms and around the hip girdles.

low mood.

lethargy.

lack of appetite and weight loss.

Rare complications

Sometimes the larger blood vessels can narrow and become blocked with inflammation and clots and if this happens, say in the heart arteries, a heart attack can occur, or if in the brain a stroke can result.

Other nervous system problems include inflammation of nerves due to blockage of the nutrient blood vessels, or noises in the ear (tinnitus), hearing loss or dizziness (vertigo). Fortunately these are rare complications.

How is GCA diagnosed?

Blood tests The doctor is alerted by the patient's history and although there is no single diagnostic test the doctor will perform some routine blood tests, in particular erythrocyte sedimentation rate (ESR). In this test blood from the patient is stood in a narrow glass tube and the red cells are allowed to settle. Normally this will be by a few millimetres in an hour but the presence of immune complexes in GCA speeds the process up. In GCA, values over 50mm in one hour would be typical. However, 2 per cent of patients with GCA will show a normal ESR.

C-reactive protein (CRP) is another marker of inflammation in the blood, and is raised in GCA but is no more helpful than ESR in either diagnosis or predicting relapse.

Further blood tests can rule out other conditions in which vasculitis also occurs. These include antibodies such as rheumatoid factor (found in rheumatoid disease) or anti-nuclear factor (found in systemic lupus erythematosus and other autoimmune conditions).

Biopsy

Often a biopsy of the temporal artery on the side of the temple is requested, but it shows the characteristic findings of inflammatory cells and damage to the lining of the artery in only 60 to 80 per cent of cases.

As a biopsy often takes several days to process and the patient's eyesight is under threat without treatment, many doctors commence treatment before the results are available or even before a biopsy is done.

Several days after starting treatment, the temporal artery biopsy may still show changes consistent with the diagnosis but many doctors will feel confident enough to make the diagnosis on the grounds of the clinical picture and a very high ESR, and omit the biopsy.

The American College of Rheumatology has devised criteria for diagnosis based on all the different aspects described here, the presence of at least three of the five main features being diagnostic of GCA.

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