Polymyalgia rheumatica (PMR) is characterised by inflammatory pain of shoulders and the pelvic girdle that affects older people. Conditions that can mimic PMR include rheumatoid arthritis (RA), spondyloarthritis (SpA) and calcium pyrophosphate disease (CPPD). In this study, we aimed to define the prevalence of CPPD among patients with polymyalgic syndrome with suspected PMR according to recent ACR/EULAR criteria.
This was an observational study in which we included patients with polymyalgic syndrome (inflammatory pain of shoulders, elevated C-reactive protein (CRP) level, and age >50 years). All patients were tested for RA antibodies and underwent ultrasonography (US) of shoulders [gleno-humeral effusion, biceps tenosynovitis, sub-acromiodeltoid (SAD) bursitis, synovitis and CPPD of the acromio-clavicular (AC) joint and humeral bone erosion].
We included 94 patients with polymyalgic syndrome (mean age 69.4±11.3 years, 67% female); 27 had a diagnosis of RA and 14 SpA. The remaining 52 were considered to have PMR according to ACR/EULAR criteria for PMR; 25 had a diagnosis of CPPD. As compared with PMR patients without CPPD, those with CPPD more frequently had humeral bone erosion (p=0.003), synovitis and CPPD of the AC joint (p<0.0001 for both) and less frequently SAD bursitis (p=0.0098). For PMR diagnosis, the most sensitive US features were SAD bursitis (96.3%) and biceps tenosynovitis (85.2%), despite low specificity. For CPPD diagnosis, CPPD of the AC joint had the best ratio of sensitivity to specificity (sensitivity: 85.2%; specificity: 97.1%).
Detection of CPPD is relatively frequent with suspected PMR. Adding US assessment of the AC joint to usual US screening might help the clinician better distinguish PMR from other conditions, notably CPPD.