Polymyalgia rheumatica (PMR) is the most common inflammatory rheumatic disease of the elderly; incidence of 700/100,000 in persons over the age of 50 years. Accurate diagnosis is difficult in PMR because proximal pain and stiffness syndrome, a commonly accepted phenotype of PMR, can occur in many other rheumatologic and inflammatory illnesses. There is significant overlap in the pathobiology of the disease with other rheumatic diseases, including synovitis, vasculitis inflammatory mechanisms and genetics.
Polymyalgia symptoms are not uncommon as presenting manifestations of a wide spectrum of systemic conditions. These include malignancies, giant cell arteritis and other forms of vasculitis, rheumatoid arthritis, seronegative spondyloarthritis, metabolic and crystalline disorders and systemic infections. Special concern about the presence of diseases different from PMR or GCA must be considered in patients presenting with atypical symptoms of PMR. Similarities in initial clinical presentation often delays diagnosis, and over time, approximately 10 to 30% of patients initially diagnosed with PMR are found to have an alternative diagnosis.
Laboratory tests tend to be unhelpful, although a positive rheumatoid factor or ACPA might indicate RA, and the presence of HLA-DRB1*04 may indicate underlying rheumatoid arthritis or giant cell arteritis. Response to corticosteroids is not a useful diagnostic test. Development of the EULAR/ACR provisional classification criteria for polymyalgia rheumatica have substantially improved disease classification and served to define the place of PMR among rheumatic diseases.
There is a trade-off between sensitivity and specificity of the criteria. From the perspective of the patient, should we err on the side of overdiagnosing, or underdiagnosing PMR? Over diagnosis means subjecting patients to unwanted side effects of corticosteroids, while underdiagnosis may mean failure to treat correctly, with the attendant consequences. The morbidity of the disease and its limited treatment options are compelling reasons for better defining the place of PMR in the spectrum of systemic rheumatic diseases.
Dasgupta B et al. American College of Rheumatology provisional classification criteria for polymyalgia rheumatica. Ann Rheumatic Dis,2012;71:484-492 doi:10.1136/annrheumdis-2011-200329 and Arthritis Rheum 2012; 64(4):943
Disclosure of Interest None declared