Study of Circulating Microparticles in Giant Cell Arteritis

For GCA group: Inclusion Criteria: * Men and women ≥ 18 years of age Patient affiliated to social security regimen * Informed and having signed the consent form to take part in the study. * Diagnosis of GCA, meeting at least 3 of the following 5 American College of Rheumatology (ACR) criteria for the diagnosis of GCA, including inflammatory syndrome and having * Either temporal artery biopsy showing characteristic GCA abnormality * Or inflammatory arteritis on imaging examination Exclusion Criteria: * Persons under protection of the court or guardianship * Inability to understand or to follow study procedures * Dementia * cancer diagnosed within the previous 5 years (except for non-melanoma skin cancer or in situ carcinoma of the cervix)non-contributory or inconclusive temporal artery biopsy * Any conditions that might interfere with MPs level: diabetes, recent endo-arterial gesture, current treatment with corticosteroids. * Participation in another ongoing clinical trial Current anticoagulant therapy * Active infectious disease