Musculoskeletal ultrasound findings in GCA with PMR and isolated PMR.

Objectives: To compare musculoskeletal ultrasound (MSUS)-defined musculoskeletal involvement between patients with isolated PMR and those with PMR symptoms in GCA and to explore the utility of MSUS findings combined with CRP levels for identifying GCA. Methods: We analysed 20 patients with GCA-PMR and 40 with PMR from a prospectively maintained MSUS registry before treatment initiation. Both shoulders and knees were assessed using greyscale (GS) and power Doppler (PD) ultrasound. Tenosynovitis, bursitis, tendinitis and ligamentitis were scored semiquantitatively. The association between ultrasound scores and serum CRP levels was evaluated. Exploratory multivariable regression analyses were performed to assess the potential utility of MSUS-based models in identifying GCA. Results: Across all assessed sites, the prevalence and severity of MSUS-defined inflammatory findings were consistently lower in the GCA-PMR group than in the PMR group. Total GS and PD scores were significantly lower in the GCA-PMR group, despite comparable CRP levels between the groups. A model combining CRP levels and total GS+PD scores yielded an area under the curve (AUC) of 0.94 for identifying GCA. A similar performance was observed with simplified models based on selected anatomical sites. Conclusions: Patients with PMR symptoms in GCA exhibited lower MSUS-defined musculoskeletal involvement than those with isolated PMR. These findings suggest that reduced musculoskeletal inflammatory burden relative to systemic inflammation may be a characteristic feature of patients with GCA presenting with PMR symptoms. MSUS findings combined with CRP levels may provide complementary information when evaluating patients with PMR for possible GCA.