Temporal (giant cell) arteritis
Giant cell arteritis (GCA) is a granulomatous arteritis affecting large and mediumsized vessels.
GCA occurs in patients over 50 years of age with familial clustering and an association with smoking. Genetic associations include HLA-DR4 and specific isoforms of intercellular adhesion molecule-1 (ICAM-1). Peaks in incidence every 5 years suggest an infective trigger.
There is a history of polymyalgia rheumatica in up to 50% of cases. Patients present with fever, severe headache and scalp tenderness over the inflamed superficial temporal or occipital arteries. On examination the temporal arterial pulsation is progressively lost as the artery becomes thickened and there may be overlying erythematous skin. Facial, jaw and mouth pain occur due to inflammation of the facial, maxillary and lingual branches of the external carotid arteries resulting in jaw claudication. Visual disturbances such as ptosis, diplopia and visual loss may occur due to inflammation of the ciliary and/or retinal arteries.
Patchy inflammation of the arterial wall interspersed with segments of normal artery; therefore, a negative biopsy does not mean that the diagnosis is excluded. Affected areas show necrosis, loss of elastic fibres and lymphocytic and occasional giant cell infiltration.
Inflammatory markers such as the ESR and CRP are very high. Temporal artery biopsy may be diagnostic (see above).
Corticosteroids are used at high doses to prevent progression to irreversible visual loss. These should be commenced immediately the diagnosis is suspected and should not be delayed by the artery biopsy. The biopsy may still be of diagnostic value up to 5 days after commencing steroids. Once the inflammatory markers have settled, the dose is gradually reduced over a period of months.