Non-alcoholic fatty liver disease (NAFLD) is a condition characterized by excessive fat accumulation, termed steatosis. Non-alcoholic steatohepatitis (NASH) comprises a subgroup of NAFLD where steatosis coexists with liver-cell injury and inflammation. This latter condition frequently leads to the accumulation of fibrosis and can progress to cirrhosis.
In 2010, NAFLD is the number one cause of abnormal liver enzymes in the United States. While over 40% of Americans have evidence of hepatic steatosis, it is believed that 30 million, nearly one in ten, may have NASH. Put into perspective, this equates roughly to the populations of the two most populous states (see image). It is important to note that only 40-50% of NAFLD cases with abnormal liver enzymes will have steatohepatitis. For a comprehensive review of the clinical features of NAFLD/NASH, check out this recent EASL Position Statement, published in Journal of Hepatology in 2009: