One of the most common causes of chronic hepatitis is the accumulation of excess fat in the liver. The condition develops gradually, typically over several years, with the intake of too many calories. Sometimes, the first sign is abnormal results on routine blood tests. A liver biopsy may be ordered in cases in which the liver is enlarged after viral or other causes of hepatitis have been ruled out. If the biopsy reveals that liver tissue is excessively fatty, inflamed, and showing signs of damage, the condition is called nonalcoholic steatohepatitis (NASH). If a fatty liver is otherwise healthy and showing no signs of inflammation or scarring, the condition is called non-alcoholic fatty liver disease (NAFLD). NASH can be severe and can lead to cirrhosis in the liver. NAFLD typically causes no long-term harm in most patients, although a small percentage will develop progressive liver damage.
Many chemical agents, including medications, industrial toxins, and herbal and dietary supplements, can cause hepatitis.   The spectrum of drug-induced liver injury varies from acute hepatitis to chronic hepatitis to acute liver failure.  Toxins and medications can cause liver injury through a variety of mechanisms, including direct cell damage , disruption of cell metabolism, and causing structural changes.  Some drugs such as paracetamol exhibit predictable dose-dependent liver damage while others such as isoniazid cause idiosyncratic and unpredictable reactions that vary among individuals.  There are wide variations in the mechanisms of liver injury and latency period from exposure to development of clinical illness.