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ESSENTIALS OF DIAGNOSIS

Giant Cell Arteritis (GCA)

  • A granulomatous vasculitis of the aorta and the main aortic branches with tropism for the extracranial tributaries of the carotid arteries.

  • The most common primary form of vasculitis in adults, with a lifetime risk after the age of 50 of 1% and 0.5% in women and men, respectively.

  • Presents with cranial signs or symptoms (eg, headaches, scalp tenderness), polymyalgia rheumatica (PMR) symptoms, constitutional symptoms, or clinical manifestations reflecting large artery involvement (eg, extremity claudication).

  • The most serious complication is blindness, which occurs in up to 20% of patients, usually before the diagnosis is made and prednisone treatment is initiated. Therefore, it is mandatory to start glucocorticoid therapy as soon as GCA is suspected to prevent irreversible vision loss.

  • Erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) levels are elevated in more than 95% of patients at disease onset.

  • Definitive diagnosis requires temporal artery biopsy or vascular imaging.

  • Most patients respond acutely to prednisone. However, relapse upon prednisone tapering is common and glucocorticoid-sparing immunosuppressive drugs (eg, tocilizumab) are needed for remission maintenance in most cases.

PMR

  • Is an inflammatory disorder of the shoulder and hip girdles that can occur as part of GCA or, more frequently, as an isolated condition (ie, primary PMR).

  • The epidemiology of primary PMR overlaps with that of GCA, but PMR is three times more common.

  • The diagnosis is primarily a clinical one, aided by the fact that most patients have elevated ESR or CRP levels.

  • The mainstay of treatment is glucocorticoids, but flares upon glucocorticoid dose reduction are common and glucocorticoid-sparing medications are sometimes required.

Giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are chronic, relapsing inflammatory conditions considered to be part of the same disease spectrum. GCA is the most common form of systemic vasculitis in adults. It is a disorder that affects the aorta and its main branches, demonstrating a predilection for the subdivisions of the extracranial carotid arteries. The most feared complication of GCA is blindness, which can be prevented in the majority of cases by early diagnosis and prompt treatment with glucocorticoids. Other complications may include aortic aneurysm, limb ischemia form arterial stenosis, and treatment-related toxicity from glucocorticoids. PMR is an arthritis and periarthritis of the shoulder and hip girdles that can occur as part of GCA or, more commonly, as an isolated condition (ie, primary PMR).

Etiology & Pathogenesis

The etiology of GCA and primary PMR is unknown, and the understanding of their pathogenesis is only partially understood. It is known, however, that these conditions share risk factors, and probably disease mechanisms as well.

The search for an infectious cause for GCA has been pursued with a number of techniques. Varicella zoster virus has been proposed as a causative agent in studies of temporal artery biopsies, but results have ...

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