Giant cell arteritis and polymyalgia rheumatica: two different but often overlapping conditions.

OBJECTIVES Giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are common and frequently overlapping diseases. In this manuscript similarities and differences between these conditions have been assessed. METHODS A retrospective review of the literature was conducted. Reports emphasizing features in common and possible differences are reviewed. RESULTS GCA and PMR are characterized by late age at disease onset, are more common in women, exhibit evidence of a systemic inflammatory response, and generally respond well to corticosteroids. In biopsy-proven GCA, PMR manifestations are observed in up to 50% of cases. PMR may be the presenting feature in patients who later develop typical cranial manifestations of GCA. However, PMR manifestations may be observed in diverse conditions other than GCA. Patients with isolated PMR are younger than those with PMR associated to biopsy-proven GCA and exhibit milder inflammatory disease as shown by significantly less abnormality in most laboratory findings. Recent observations have shown that the frequency of pathologic features of GCA in temporal artery biopsies of patients with clinically isolated PMR is less than that previously reported. Besides different steroid requirements, GCA is associated with more vascular complications. Genetic differences, in particular different HLA-DRB1 associations, also have been observed. CONCLUSIONS Polymyalgia manifestations may be observed in patients with biopsy-proven GCA, but isolated PMR may be the only clinical feature or the phenotypic expression of a number of conditions. Clinical features and immunogenetic studies show subtle differences between GCA and PMR.