Polymyalgia rheumatica (PMR) is an inflammatory disease of the elderly characterized by the nonspecific findings of girdle pain and stiffness and constitutional symptoms: as a result its differential diagnosis ranges from rheumatic, to infective and neoplastic diseases. PMR patients also often show peripheral arthritis, which fact further complicates the diagnosis. The main differential diagnosis in patients with suspected PMR is EORA, which also may present with girdle pain and raised inflammation. Both conditions also share a common genetic background and patients with cured PMR can relapse as EORA. Many studies have addressed clinical and laboratory discriminating clues, with only peripheral arthritis being effective. However, peripheral arthritis, being present in up to 40% of PMR patients, has a poor predictive value. In a recent study, US clues for the diagnosis of PMR were the presence of subacromial-subdeltoid bursitis, low frequency of knee menisci chondrocalcinosis and low power Doppler scores at the wrist. Conversely, effusion and synovitis of wrist, metacarpophalangeal joints, metatarsophalangeal joints, and tendinous calcaneal calcifications or Achilles enthesitis were more frequent in patients with diagnoses other than PMR.
In a study with 18F-FDG positron emission/computed tomography (PET/CT), PMR patients showed higher uptake of the ischiatic, trochanteric and interspinous bursae compared to EORA patients. Shoulders were not evaluated because of their anatomical complexity and the difficulty of precisely localizing inflammation. In the clinic, follow-up over time is often the only way to help differential diagnosis: if glucocorticoid treatment is effective despite its tapering and peripheral arthritis does not become chronic, the diagnosis of PMR is likely to be correct.
Disclosure of Interest None declared