18th January 2024

Giant Cell Arteritis

Background

Giant Cell Arteritis (or GCA) is a large vessel vasculitis causing granulomatous inflammation of the aorta and larger branches. Cranial GCA (or Temporal Arteritis) is the most common form and will be the focus of this section.

GCA is more common in females (ratio 2:1) and in patients aged >50 years– presentation in younger age is extremely rare. Prompt recognition and treatment of GCA is vital given the risk of ophthalmic involvement, which can lead to permanent visual loss.

Association with Polymyalgia Rheumatica

GCA is closely associated with Polymyalgia Rheumatica (PMR), another large vessel vasculitis; some consider the two conditions to be a spectrum of the same disease process with variable expression. Roughly half of patients with GCA have symptoms of PMR, and a fifth of patients with PMR have evidence of GCA. Genetic susceptibility to both conditions is found in those carrying the HLA DRB1*04 and DRB*01 genes. Those carrying this gene are at higher risk of complications and treatment resistance.

Clinical presentation

GCA classically presents with the following, either acutely or sub-acutely:

Symptoms

• Temporal headache – usually unilateral but can be bilateral
• Scalp tenderness
• Intermittent claudication to the jaw/tongue – pain on chewing, which resolves on rest
• Constitutional symptoms – fatigue, night sweats, weight loss, anorexia, low-grade fever
• Visual disturbance – flashers/floaters, diplopia, changes in colour vision and in severe cases visual loss
• Features of PMR – proximal muscle pain and stiffness
• Neurological features such as TIA or upper cranial nerve palsies

Signs

• Temporal artery tenderness, thickening, nodularity or ulceration
• Pallor and oedema of the optic disc on fundoscopy

Investigations

Confirming the diagnosis is vital, and the gold standard is currently temporal artery biopsy. Colour duplex ultrasonography has also been shown to be effective in diagnosing GCA and is gaining popularity due to being non-invasive and more easily available.

Other expected findings would be:

• Raised ESR/CRP
• Normocytic, normochromic anaemia
• Thrombocytosis
• Deranged liver function tests, in particular, a raised ALP

Histology

Histology of the temporal artery shows an occlusive vasculopathy with intimal proliferation and a reduction in diameter of the lumen. Inflammation is patchy (skip lesions); therefore, a normal biopsy cannot rule out GCA. The inflammatory infiltrate is predominantly composed of macrophages and CD4 lymphocytes. Only half of positive histological samples demonstrate giant cells.

Management 

All patients with suspected GCA should be referred for urgent specialist assessment, but this should not delay initiation of treatment.

Treatment involves steroids, as follows:

• 40mg Prednisolone daily, unless the patient has ischaemic symptoms
• 60mg Prednisolone daily in the presence of ischaemic symptoms, i.e. jaw claudication/visual loss
• Admission for IV Methylprednisolone may be indicated in the presence of visual symptoms (along with urgent ophthalmic assessment)

After resolution of symptoms, steroids can be tapered, and this is often a long and protracted process. Relapses are common and respond to increasing the dose back up to the last effective dose. If steroids are ineffective or not tolerated, methotrexate or tocilizumab (IL-6 inhibitor) may be considered by rheumatologists.

Complications

GCA is considered a medical emergency due to the risk of severe complications, particularly if it is not treated in a timely manner. The following complications may occur:

• Visual loss (due to anterior ischemic optic neuropathy)
• Dissections or aneurysms of the aorta or its branches
• Stroke

References

• Tidy C. Giant cell arteritis (temporal arteritis) [Internet]. Patient.info. 2022 [cited 2023 Feb14]. Available from: https://patient.info/doctor/giant-cell-arteritis-pro
• Hernández-Rodríguez J, Murgia G, Villar I, Campo E, Mackie SL, Chakrabarty A, et al. Description and validation of histological patterns and proposal of a dynamic model of inflammatory infiltration in giant-cell arteritis. Medicine. 2016;95(8).