Monitoring Disease Activity in Patients With Takayasu Arteritis With the OMERACT Takayasu Ultrasound Score (OTUS)

Inclusion Criteria: * Age ≥18 years * Male and female * Diagnosis of TAK according to the 1990 ACR and/or 2022 ACR/EULAR classification criteria * Active disease, defined as the presence of at least two of the following three domains: * Clinical domain: new onset or worsening of clinical signs and/or symptoms attributable to TAK; * Laboratory domain: elevation of inflammatory markers, defined as ESR and/or CRP above the upper limit of normal according to local laboratory standards, not attributable to causes other than TAK; * Imaging domain: imaging evidence of active vasculitis on modalities other than ultrasound, including FDG-PET, magnetic resonance angiography (MRA), or computed tomography angiography (CTA). * Ability to undergo serial vascular ultrasound assessments during follow-up * Provision of signed informed consent Exclusion Criteria: * Inability or contraindication to undergo vascular US * Severe comorbidities limiting participation or follow-up * Concomitant conditions that may confound ultrasound findings (e.g., significant atherosclerosis requiring intervention, complete occlusion of one of the arterial segments under investigation) * Diagnosis of another rheumatologic disease * Refusal or inability to provide informed consent