Objective: To investigate the inflammatory involvement of shoulder articular and extraarticular structures in polymyalgia rheumatica (PMR) patients with a normal erythrocyte sedimentation rate (ESR) at diagnosis.
Methods: This was a case-control study. All consecutive, untreated new outpatients diagnosed as having PMR with a normal ESR (<40 mm/hour) during a 6-month period were included in the study (case patients). Controls were 12 consecutive, untreated PMR outpatients with an ESR of >40 mm/hour who were observed after the case patients. Before starting corticosteroid therapy, all case patients and controls underwent bilateral shoulder ultrasonography (US) and magnetic resonance imaging (MRI). US and MRI scans were evaluated independently by two radiologists who were blinded to the reciprocal results.
Results: Six case patients (4 men and 2 women) and 12 controls (4 men and 8 women) were studied. Both US and MRI demonstrated bilateral subacromial/subdeltoid bursitis in all 6 case patients and in 11 of the 12 (92%) controls (P not significant [NS]). One control had unilateral bursitis. Glenohumeral joint synovitis was found in 4 of 6 case patients (67%) by MRI and in 3 of 6 case patients (50%) by US (P NS), as well as in 8 of 12 controls (67%) by MRI and in 7 of 12 controls (58%) by US (P NS). Both MRI and US detected biceps tenosynovitis in 5 of 6 case patients (83%) and in 8 of 12 controls (67%) (P NS). The severity of bursitis did not differ significantly between the groups. US was as effective as MRI in detecting inflammatory changes of the shoulder.
Conclusion: MRI and US studies showed that PMR patients with normal or high ESRs have similar inflammatory shoulder lesions. Moreover, bilateral subacromial/subdeltoid bursitis represents the imaging hallmark in PMR patients with a high or normal ESR. MRI or US of the shoulder may facilitate the proper diagnosis in patients with the typical proximal symptoms of PMR who also have normal ESRs.