In the United States, GCA affects about 18 out of 100,000 people older than 50 years. The epidemiologic-demographic characteristics of GCA are similar to those of PMR. The incidence of GCA is much higher in the northern latitudes, with a mean age at onset of 74 years. GCA and PMR likely represent extremes of a disease spectrum, with many patients presenting with features of both diseases. Approximately 40% of GCA patients have concurrent features of PMR at some point during their disease course.