EASL Clinical Practice Guidelines

Epidemiology of AIH

AIH is an non-resolving chronic liver disease that affects mainly women and is characterized by hypergammaglobulinaemia even in the absence of cirrhosis, circulating autoantibodies, association with human leukocyte antigens (HLA) DR3 or DR4, interface hepatitis on liver histology, and a favourable response to immunosuppression [[2], [3], [4], [5]]. The disease, if untreated, often leads to cirrhosis, liver failure and death.

AIH is considered relatively rare, as its prevalence ranges from 16 to 18 cases per 100,000 inhabitants in Europe [[6], [7], [8], [9], [10], [11]]. Until recently, the incidence and prevalence of AIH on a population-based level was assessed in only two studies [[6], [9]]. Interestingly however, higher prevalence rates have been reported in areas with quite stable populations. For instance, prevalence rates of 42.9 cases per 100,000 and 24.5 cases per 100,000 inhabitants have been reported in Alaska natives [12] and New Zealand [9], respectively. In addition, a large Danish nationwide population-based study assessed the incidence and prevalence of AIH in Denmark during a nearly 20 year time period ranging from 1994 to 2012 including 1721 AIH patients [13]. The most striking observation in that study was the marked increase in AIH incidence over time, which could not be attributed to a relative change in case ascertainment rates. Actually, the incidence rate of AIH in Denmark has nearly doubled between 1994 to 2012, reaching a point prevalence in 2012 of 24/100,000 (35/100,000 for females) [13].

AIH prevalence and clinical expression seem to vary according to ethnicity. Alaskan natives appear to have a high frequency of acute icteric disease at the disease onset [12], and the disease is more common and more severe in North American Aboriginal/First Nations populations compared with predominantly Caucasian, non-First Nations populations [14]. African-American patients more commonly have cirrhosis, a higher frequency of treatment failure and higher mortality than white American patients [[15], [16]]. Mexican Mestizos commonly show cirrhosis at initial evaluation [17] and patients of Hispanic origin are characterized by an aggressive presentation both biochemically and histologically with a very high prevalence of cirrhosis and cholestatic features [[18], [19]], whereas patients of Asian or other non-European Caucasoid background have very poor outcomes [[18], [20]]. Although most of the above mentioned studies are retrospective and have been performed in tertiary centres, these observations have led to the assumption that AIH has diverse clinical phenotypes and outcomes in different ethnic groups within a country and between countries. These differences may reflect genetic predispositions, indigenous etiological agents, and/or pharmacogenomic mechanisms, but they might also be primarily due to complex socioeconomic reasons such as variations in the delivery of health care, delayed diagnosis as well as competing risk factors [21].