To demonstrate that microparticles (MPs), having a powerful procoagulant potential, are in larger amounts in the blood of patients with histologically proven giant cell arteritis (GCA), compared with patients matched for age, sex and with or without inflammatory syndrome.

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

primary and secondary care hospital