Are polymyalgia rheumatica and giant cell arteritis the same disease?

Objective: To summarize the evidence about the relationship between polymyalgia rheumatica (PMR) and giant cell arteritis (GCA). Methods: Review of relevant articles from the English-language literature. Results: Epidemiologic studies suggest that PMR and GCA are closely related conditions affecting people over 50 years and frequently occurring in the same patient. PMR symptoms have been observed in 40 to 60 percent of GCA clinical series. Also, temporal artery biopsy may yield positive results for GCA in patients with isolated PMR. Conflicting HLA-DRB1 genotype results have been reported, and recent studies have shown that PMR and GCA have different expression of RANTES, TNFalpha microsatellite, and IL-6 promoter genetic polymorphisms. Search for a possible common infectious agent have yielded disappointing results. Although parvovirus B19 DNA is present in the artery wall of patients with GCA, this virus may be only an innocent bystander. Cytokine studies on a limited number of temporal artery biopsy specimens have shown that interferon-gamma is produced in GCA and not in PMR, suggesting that this cytokine may be crucial to the development of overt vasculitis. Conclusions: PMR and GCA frequently occur together but no definitive conclusions can be drawn about the nature of this association.