Pilot Study to EvaluateThrombomodulin to Rule Out Giant Cell Arteritis (GCA) in Polymyalgia Rheumatica (PMR) Patients. (THROPIQ)

Inclusion Criteria:

• Patient who has given oral consent

• Patient > 50 years of age

Patients with PPR, meeting ACR/EULAR 2012 criteria:

• age > 50 years at onset of symptoms

• inflammatory limb-girdle pain

• elevated ESR (>20 mm/hr) and/or CRP (> 10 mg/l)

• AND Score ≥ 4 points among

• Morning stiffness > 45 minutes (2 pts)

• Hip pain or limitation of amplitude (1 pt)

• Rheumatoid factor or anti-CCP antibodies negative (2 pts)

• Absence of other joint pain (1 pt)

Patient with suspected GCA requiring diagnostic work-up. Suspicion of GCA will be based on:

• The presence of at least one clinical sign of GCA (temporal headache, temporalartery abnormalities, jaw claudication, scalp hyperesthesia, visual disturbance).

• OR the presence of a significant inflammatory syndrome defined by CRP > 100 mg/L ora ESR > 100 mm/hr

Exclusion Criteria:

• Patient not affiliated to national health insurance

• Patient under legal protection (curatorship, guardianship)

• Patient subject to a measure of legal safeguard

• Pregnant or breast-feeding women

• Adult patient unable to provide consent

• Patient having received corticosteroid or immunosuppressive treatment in the monthprior to inclusion

• Patient with a contraindication to corticosteroid therapy

• Patients with an active infection, neoplasia or other inflammatory/autoimmunecondition

• Patients with late onset rheumatoid arthritis.

• Conditions rendering vascular imaging unfeasible or uninterpretable:

• For angio-CT: allergy to iodine, renal failure (CKD <30 mL/min)

• For PET scan: unbalanced diabetes NB: only one of the two vascular imagingtechniques will be performed, depending on the patient&#39;s condition and thetechnical resources available.

Secondary exclusion criteria:

• Final diagnosis of paraneoplastic PMR

• Final diagnosis of RA

• Negative PET scan (if performed 72 hours after glucocorticoid introduction)