Page 338 - The Vasculitides, Volume 1: General Considerations and Systemic Vasculitis

312 Vanessa Quick and John Kirwan

This chapter reviews the epidemiologic, clinicopathologic features, diagnosis and treatment of
giant cell arteritis.

Overview

The clinical symptoms in GCA are usually due to inflammation of the medium sized
extra-cranial branches of the carotid artery, particularly the superficial temporal division [7].
About one-half the time, GCA is accompanied by aching and stiffness of the shoulder and hip
girdles typical of polymyalgia rheumatica (PMR). Unfortunately neither the classical clinical
presentation nor the combinations of clinical symptoms and signs predictive of a definite
diagnosis of GCA occur commonly [8]. Visual loss in one or both eyes can be averted by
early diagnosis and prompt treatment [9]. Temporal artery biopsy (TAB) is the gold standard
of diagnosis, perhaps guided by non-invasive temporal artery ultrasound (TAUS).
Glucocorticoids (corticosteroids) remain the best treatment for GCA with similar long-term
survival rates as age-matched population controls [10]. There are no randomized clinical trial
(RCT) data in GCA to decide the correct glucocorticoid dose regimen. Recent international
guidelines [11, 12] provide assistance in diagnosis and treatment although the evidence base
is weak and the guidance is at best advisory. The introduction of GCA care pathways may
improve patient outcome [13, 14].

Epidemiology

The lifetime risk of developing GCA is estimated at 1% for women and 0.5% for men
[15]. The disease rarely occurs in individuals under the age of 50 years and peaks in the
eighth decade of life. It more commonly affects Scandinavians and North Americans of
Scandinavian decent than Southern Europeans [16], and occurs rarely in Black and Asian
populations [17-20]. Such racial patterns together with familial aggregation [21] point to a
genetic predisposition to the disease. There is an association with the HLA-DRB1*04 allele
[7, 22].

The geographical variation and seasonal fluctuation of GCA in turn suggests a
contribution from environmental and infectious factors [23] although definite links to
particular microorganisms or vaccinations [24-26] have not been established. Moreover, there
is no evidence that GCA occurs with increased prevalence in association with malignancy or
as a paraneoplastic syndrome [27]. GCA is likely a polygenic disease wherein multiple
environmental and genetic factors influence susceptibility and severity [28].

Pathology

The classical histological changes of GCA include arterial wall inflammation, internal
elastic lamina fragmentation and intimal thickening (Figure 1). Although GCA derives its
name from the presence of multinucleated giant cells, the latter are seen in only about one-
half of positive TAB, albeit in association with a granulomatous inflammatory infiltrate

Complimentary Contributor Copy