Large Vessel Vasculitides (including Polymyalgia Rheumatica)

Abstract

Abstract The most important large vessel vasculitides are giant cell arteritis (GCA) and Takayasu's arteritis. These are similar but distinct idiopathic diseases characterized by constitutional symptoms with raised inflammatory markers in the blood and underlying granulomatous large vessel vasculitis. The two conditions are distinguished predominantly by the nature of the vessels involved and the resultant clinical presentation. Polymyalgia rheumatica (PMR) is a syndrome that may precede GCA. There is clinical and histological overlap between these two conditions, which can be considered opposite ends of a disease spectrum, but their management differs and thus they are discussed separately in this contribution. Pathology – both GCA and Takayasu's arteritis are associated with panarteritis of large and medium vessels involving lymphocytes, macrophages and multinucleate giant cells. The inflammation starts with infiltration of the adventitia and progresses inwards, involving the media and resulting in extensive fragmentation of the internal elastic lamina. Intimal proliferation is found but fibrinoid necrosis is uncommon. Healing with replacement of elastic tissue by fibrosis, obliteration of the vasa vasorum and irregular thickening of the intima occurs particularly in Takayasu's arteritis. This can result in stenosis, dilatation and/or aneurysm formation. Recanalization of occluded vessels is common. Differential diagnosis – distinguishing GCA from simple PMR can be difficult because the conditions overlap and can coexist. Focal symptoms and signs suggesting vessel ischaemia in association with nonspecific PMR features and a high acute phase response strongly suggest GCA and the need for high-dose corticosteroids to prevent irreversible ischaemic damage. Distinguishing GCA from Takayasu's arteritis is helped by differences in age group affected and expression of disease. GCA is usually more corticosteroid responsive and has a less protracted course than Takayasu's arteritis. Other differential diagnoses are listed in Figure 1.