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DIAGNOSIS OF GIANT CELL ARTERITIS. The diagnosis of giant cell arteritis (GCA) must be made promptly in order to initiate appropriate treatment aimed at relieving symptoms and avoiding ischemic complications, particularly visual ones. The diagnosis of GCA is based on the occurrence, in a patient over 50, of clinical signs of GCA, primarily recent headaches, or polymyalgia rheumatica, as «evidence» of large-vessel vasculitis, which is provided by histological analysis of an arterial fragment, usually the temporal artery, or by imaging of the cephalic arteries, the aorta and/ or its main branches by Doppler US scan, angio-CT, 18fluorodeoxyglucose PET scan or more rarely by MRI angiography. In addition, in more than 95% of cases, patients have an elevation in markers of inflammatory syndrome. This is less marked in the case of visual or neurological ischemic complications. Two main GCA phenotypes can be distinguished: on the one hand, cephalic GCA, in which cephalic vessel involvement predominates and which identifies patients at the greatest risk of ischemic complications; on the other hand, extracephalic GCA concerns younger patients with a lower ischemic risk but with more aortic complications and more frequent relapses. The establishment «fast track» type structures in specialized centers allows for rapid management in order to identify patients to be treated in order to avoid ischemic complications and to quickly perform the necessary examinations to confirm the diagnosis and ensure that the patient receives appropriate management., Competing Interests: H. Greigert déclare n’avoir aucun lien d’intérêts. B. Bonotte déclare des interventions ponctuelles pour Roche Chugai, Amgen, Novartis, LFB, Boehringer Ingelheim, Eusa Pharma et avoir été pris en charge à l’occasion de déplacement pour congrès par Novartis, Otsuka, AstraZeneca. M. Samson déclare des interventions ponctuelles pour Roche Chugai, Novartis, Vifor Pharma, AbbVie, Argenx, GSK et avoir été pris en charge à l’occasion de déplacement pour congrès par Roche Chugai, AbbVie, Novartis, Vifor Pharma, GSK.

TREATMENT OF GIANT CELL ARTERITIS. The treatment of giant cell arteritis (GCA) is based on glucocorticoids. This treatment significantly reduces the risk of ischemic complications, especially those of a visual nature, rapidly relieves the symptoms of the disease, and eliminates the inflammatory syndrome. The diagnosis of GCA must be able to question if corticosteroid therapy is ineffective. Once the symptoms have resolved and the inflammatory syndrome has normalized, glucocorticosteroids are tapered very gradually. The goal is to discontinue glucocorticosteroids in 12 to 18 months. Nearly half of patients experience flares during the glucocorticoid taper. These are usually benign, not visually life-threatening, and easily controlled by increasing glucocorticoids. However, these relapses contribute to prolonging the treatment duration and thus the cumulative dose of glucocorticoids received by patients, which leads to the occurrence of adverse effects of glucocorticoids in almost all patients. For this reason, it is sometimes necessary to prescribe glucocorticoid-sparing treatments, particularly methotrexate and tocilizumab. The efficacy of these treatments and others in development is essential and to be discussed. In addition, the management of patients with GCA should include preventive measures to reduce cardiovascular, infectious and osteoporosis risks., Competing Interests: M. Samson déclare des interventions ponctuelles pour Roche Chugai, Novartis, Vifor Pharma, AbbVie, Argenx, GSK et avoir été pris en charge à l’occasion de déplacement pour congrès, par Roche Chugai, AbbVie, Novartis, Vifor Pharma, GSK. H. Greigert déclare n’avoir aucun lien d’intérêts. B. Bonotte déclare des interventions ponctuelles pour Roche Chugai, Amgen, Novartis, LFB, Boehringer Ingelheim, Eusa Pharma et avoir été pris en charge à l’occasion de déplacement pour congrès par Novartis, Otsuka, AstraZeneca.

Competing Interests: M. Samson déclare des interventions ponctuelles pour Roche Chugai, Novartis, Vifor Pharma, AbbVie, Argenx, GSK et avoir été pris en charge à l’occasion de déplacement pour congrès par Roche Chugai, AbbVie, Novartis, Vifor Pharma, GSK. H. Greigert déclare n’avoir aucun lien d’intérêts. B. Bonotte déclare des interventions ponctuelles pour Roche Chugai, Amgen, Novartis, LFB, Boehringer Ingelheim, Eusa Pharma et avoir été pris en charge à l’occasion de déplacement pour congrès par Novartis, Otsuka, AstraZeneca.

EPIDEMIOLOGY AND PATHOPHYSIOLOGY OF GIANT CELL ARTERITIS. Giant cell arteritis (GCA) is a granulomatous vasculitis. It affects patients over 50 years of age, predominantly women. The pathophysiology of GCA involves genetic and environmental factors leading to the development of inflammation and subsequent large artery wall remodelling, the mechanisms of which are increasingly understood. The process is thought to begin with the activation of dendritic cells in the vessel wall. These then recruit and activate CD4 T cells, inducing their proliferation and polarisation into Th1 and Th17 cells, which produce interferon-gamma (IFN-γ) and interleukin-17 (IL-17) respectively. IFN-γ activates vascular smooth muscle cells, which produce chemokines that induce the recruitment of other mononuclear cells (CD4 and CD8 T cells and monocytes). This inflammatory infiltrate, the differentiation of monocytes into macrophages induce the production of other mediators that cause remodeling of the vascular wall based on destruction of the arterial wall, neoangiogenesis and intimal hyperplasia. This remodelling leads to the ischaemic manifestations of GCA by causing stenosis or even occlusion of the affected vessels. More recently, mechanisms have been identified that allow the perpetuation of inflammation and vascular remodelling, explaining the chronic evolution of GCA., Competing Interests: H. Greigert déclare n’avoir aucun lien d’intérêts. B. Bonotte déclare des interventions ponctuelles pour Roche Chugai, Amgen, Novartis, LFB, Boehringer Ingelheim, Eusa Pharma et avoir été pris en charge à l’occasion de déplacement pour congrès par Novartis, Otsuka, AstraZeneca. M. Samson déclare des interventions ponctuelles pour Roche Chugai, Novartis, Vifor Pharma, AbbVie, Argenx, GSK et avoir été pris en charge à l’occasion de déplacement pour congrès par Roche Chugai, AbbVie, Novartis, Vifor Pharma, GSK.