Diagnosing late onset rheumatoid arthritis, polymyalgia rheumatica, and temporal arteritis in patients presenting with polymyalgic symptoms. A prospective longterm evaluation.

OBJECTIVE: . To examine for demographic and clinical differences between late onset rheumatoid arthritis (LORA), polymyalgia rheumatica (PMR), and temporal arteritis (TA) patients presenting with polymyalgic symptoms (PMS) and to identify baseline clinical and laboratory features that would lead to a more accurate final diagnosis.
METHODS: Three hundred forty-nine consecutive patients with new onset of symptoms suggestive of LORA, PMR, or TA presenting at or above age 60 years were enrolled in a prospective study.
RESULTS: During followup, 9 patients diagnosed initially as PMR developed LORA (giving a final total of 145), 5 patients initially diagnosed as LORA changed diagnosis to PMR (final total 147), and 29 patients had PMS that predated TA symptoms (final total 57). The delay in diagnosis ranged from 1 to 30 months. DRB1*04 was associated with development of both LORA and TA.
CONCLUSION: In about 10% of patients the correct diagnosis of LORA, PMR, and TA in those presenting with PMS may be delayed due to similarities in initial clinical presentation. Longterm followup is essential to establish correct diagnosis. Laboratory tests tend to be unhelpful, although a positive rheumatoid factor or persistently raised plasma viscosity despite steroids might indicate RA, and the presence of HLA-DRB1*04 may indicate underlying RA or TA.