Musculoskeletal magnetic resonance imaging findings support a common spectrum of giant cell arteritis and polymyalgia rheumatica

To investigate the proportion and distribution of contrast enhancement (CE) of musculoskeletal structures with MRI of the thorax/abdomen/pelvis in giant cell arteritis (GCA). CE at 34 musculoskeletal sites was rated with a four-point ordinal scale. Patients were divided into groups with or without glucocorticoid (GC) treatment and with or without symptoms of polymyalgia rheumatica (PMR). Two composite scores were created: an MRI score, including seven sites, and a limited MRI score, including four sites. Retrospectively, 90 consecutive patients with GCA were included. The population included 54 and 36 patients with and without PMR symptoms, respectively, and 45 (50%) patients were receiving GCs at the time of MRI. CE was found in 90.7% of lumbar spines, 87.5% of the pelvis, 82.2% of shoulder girdles and in 95.6% at any site in patients without GCs. The proportion of patients without and with GCs with at least moderate enhancement was, respectively, 91.1% and 75.6% at ≥1-3 sites, 75.6% and 51.1% at ≥4-6 sites, and 64.4% and 28.9% at ≥7-9 sites. The mean difference between the proportion of pathological CE in patients with and without GCs was 27.4% for synovial sites and 18.3% for periarticular/musculotendinous sites. Both composite scores captured substantial differences between groups, and correlation was very strong between scores. MRI shows CE of musculoskeletal structures typical of PMR in most patients with GCA, supporting the concept of 'GCA-PMR spectrum disease'. Changes are more frequent at periarticular/musculotendinous sites and in the presence of PMR symptoms. A clear response to GCs is evident, less so for periarticular/musculotendinous sites.