29th January 2024

Giant cell arteritis (temporal arteritis)

Background 

Epidemiology 

Giant cell arteritis (GCA) or temporal arteritis is the most common form of vasculitis in adults. Almost all patients with GCA are over the age of 50, with a peak incidence of 70-90 years of age. There is a female predominance. Although it can occur in all racial groups, it is most common in people of Scandinavian descent. Around 22 people per 100,000 aged over the age of 50 will develop GCA.

Aetiology

The exact cause of the condition is unknown. Possible contributing factors include genetic predisposition (e.g. human leukocyte antigen HLA-DR4) and viral infections (e.g. parvovirus B19). Up to 50% of patients with giant cell arteritis also have polymyalgia rheumatica (PMR).

Pathophysiology

The activation of dendritic cells in the blood vessel walls leads to the recruitment of lymphocytes and monocytes. The differentiation of monocytes into macrophages and giant cells augments the inflammatory process by producing cytokines. This process leads to the destruction of vessel wall structures and concentric intimal hyperplasia. There is resultant reduction in blood flow and ischaemia. GCA commonly involves external carotid artery branches (especially temporal artery), as well as the aorta and vertebral arteries.

Clinical features

Patients can commonly present with non-specific constitutional symptoms such as fever, weight loss, night sweats, malaise, fatigue, myalgia and arthralgia (mainly of the shoulders and hip joints). 

Other features include those specific to arterial inflammation, such as new onset unilateral or bilateral headache. This is typically over the temples, which can be pulsatile, throbbing or dull in nature. Other symptoms include jaw claudication (jaw pain when chewing) and vision loss, which can present with scintillating scotoma, amaurosis fugax or even permanent loss of vision. Clinical examination may reveal hardened or tender temporal artery. 

Those with large vessel GCA involving the aorta and its primary branches may present with angina pectoris/acute coronary syndrome, abdominal pain or limb claudication. Signs may include asymmetrical pulses and blood pressure readings, vascular bruits, aortic regurgitation murmur and features of aortic aneurysm or dissection. 

Patients with co-existing PMR may present with symptoms of this, such as pain and stiffness of the shoulders or hips with associated limitations on movement. 

Diagnosis

If GCA is highly suspected, it is crucial not to delay the initiation of high-dose glucocorticoids to minimise the risk of vision loss. Initial laboratory tests such as low red cell count and raised ESR and CRP can be suggestive of the disease. 

Doppler ultrasound of the temporal arteries is the first line imaging technique for suspected GCA. Oedema and thickening of the vessel wall (halo sign), non-compressible artery (compression sign) and stenosis and occlusion of the vessels are all supportive of the diagnosis. However, this is operator-dependent, and other modalities such as high-resolution MRI, MRA, CTA, and PET scans can also be used. 

The gold standard for diagnosis is a temporal artery biopsy. Typical findings include panarteritis, proliferation of the intima and subsequent stenosis of the artery, necrosis of the media, and mononuclear infiltration of the vessel wall with formation of the giant cells. Despite this, histopathology may be falsely negative due to skip lesions and biopsy of the contralateral temporal artery may be required. 

Patients with PMR with no symptoms of GCA above the neck can be diagnosed clinically without a temporal artery biopsy.

Treatment

High-dose glucocorticoid therapy (prednisolone 40-60mg once a day) for 2-4 weeks is indicated for all newly diagnosed and recurrent disease. Most patients improve dramatically within 1-3 days. However, blindness is usually irreversible, which highlights the importance of early detection and treatment. Prednisolone is then tapered down to a maintenance dose to control the symptoms, generally up to 2 years. Rarely, steroid-sparing therapies such as methotrexate can be used in patients who do not respond, relapse or are at high risk of complications from long-term steroid therapy. PMR generally responds well to low-dose prednisolone. 

References

• Giant Cell Arteritis, Johns Hopkins Vasculitis Center. Available at: https://www.hopkinsvasculitis.org/types-vasculitis/giant-cell-arteritis/ [Accessed 16th January].
• Vasculitides, Amboss. Available at: https://www.amboss.com/us/knowledge/Vasculitides/ [Accessed 17th January 2022].