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

Polymyalgia rheumatica (PMR) is characterized by muscle pain in the shoulders and pelvis, increased erythrocyte sedimentation rate (ESR, an index of the speed at which red blood cells settle), absence of inflammatory joint disease or muscle disorders, and immediate resolution after treatment with low doses of corticosteroids. Giant cell or temporal arteritis (GCA) is the inflammation of the arteries. The development of PMR and GCA is not well understood, but may be influenced by genetic factors. The incidence of these two disorders is high in Sweden, Denmark, and Minnesota, which has a large proportion of persons of northern European descent, but has been observed to be low in more southern areas, such as Israel, Italy, Tennessee, and Department Loire-Atlantique, France. Environmental factors, such as infective organisms, sunlight, and contact with birds, may contribute to the development of these diseases. In addition, certain genetic and environmental factors may increase the risk of developing PMR and GCA in different populations. Studies have shown that PMR with or without GCA is associated with the presence of the human leukocyte antigen (HLA)-DR4. HLAs are histocompatibility antigens, or genetic elements that are present on all cells with a nucleus. The histocompatibility antigens are capable of provoking an immune response, and specific HLAs have been associated with certain diseases. The epidemiology of PMR and GCA and the frequency of the HLA-DR4 antigen were assessed in a Mediterranean population. PMR and/or GCA was diagnosed in 99 patients from Reggio Emilia, Italy over a nine-year period. The yearly incidence of PMR was 12.7 per 100,000 and for GCA, 6.9 per 100,000. HLA-DR4 was not significantly associated with the development of PMR and GCA. The immune and genetic aspects of PMR and GCA and their relation to the epidemiology of these disorders are discussed. (Consumer Summary produced by Reliance Medical Information, Inc.)