How are Polymyalgia Rheumatica and Giant Cell Arteritis related?
These two disorders frequently occur together in individual patients. In fact, PMR has been noted in 40% to 60% of patients with GCA and may be the initial symptom in 20% of cases. Conversely, GCA occurs in at least 15% of patients with PMR. Notably, temporal arteritis has been found on biopsy in 9% of PMR patients who did not have any clinical evidence of vasculitis. Additionally, positron emission tomography scans have shown increased uptake in the aorta in 30% of PMR patients suggesting subclinical arteritis. The clinical significance and outcome of this occult GCA in patients with PMR is unclear. The association between PMR and GCA is so strong that many have speculated that they represent the same disease but with differing severity.