Epidemiologic and immunogenetic aspects of polymyalgia rheumatica and giant cell arteritis in northern Italy

Abstract We studied the epidemiology of giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) in a Mediterranean population. Ninety‐nine patients with PMR and/or GCA were identified over a 9‐year period (1980–1988) in Reggio Emilia, Italy. The average annual incidence of PMR and GCA was 12.7/100,000 and 6.9/100,000, respectively, in a population aged 50 years or older. Frequencies of HLA antigens were determined in 49 patients with PMR and/or GCA who were followed by staff at our rheumatology unit during the 1980–1988 period. When compared with HLA findings in 242 healthy controls, DR4 was not found to be significantly associated with PMR (24% in PMR patients versus 14% in controls). Patients with GCA also showed an increased frequency of DR4 compared with controls (36% versus 14%), but this difference was also not statistically significant. The immunogenetic features of PMR and GCA and the relationship between the immunogenetic and epidemiologic patterns in different populations are discussed.