The geoepidemiology of primary biliary cirrhosis: contrasts and comparisons with the spectrum of autoimmune diseases.

Recent data have suggested that the prevalence of many autoimmune diseases is higher than originally suspected. Indeed, the incidence of some autoimmune diseases may be increasing. Part of the problem in these latter two issues is that there is a dearth of well-designed and controlled epidemiologic studies, and often confounding variables in diverse populations and geographic areas that are not well controlled. Primary biliary cirrhosis (PBC) is a highly directed, organ-specific autoimmune disease that results in the destruction of intrahepatic bile ducts. It is primarily a disease of middle-aged women. Although there is no obvious association with MHC class I or class II alleles, the relative risk of a family member of a first-degree relative within a family having a member with PBC is a hundred-fold that of the general population. Unfortunately, most epidemiologic studies have been descriptive, providing incidence and prevalence rates with many methodologic problems, including lack of an appropriate case definition, varying criteria for inclusion of cases, and inaccurate estimate of the time period to which the rate applies. Because PBC is a very definable disease with significant clinical and serologic overlaps among patients throughout the world, we believe that a review of the geoepidemiology of PBC is not only specifically of value to workers interested in autoimmune liver disease, but also of generic interest in the study of autoimmune disease. In this review, we discuss the nature of the existing epidemiologic data and the possible roles of genetic and environmental factors in the etiology of the disease and compare such data to similar observations for multiple sclerosis, systemic lupus erythematosus, and rheumatoid arthritis.