Histology of Nonalcoholic Fatty Liver Disease and Nonalcoholic Steatohepatitis in Adults and Children.

Nonalcoholic fatty liver disease (NAFLD) is the liver disease associated with obesity, diabetes, and the metabolic syndrome. Although steatosis is a key histologic feature, liver biopsies of patients with NAFLD can show a wide range of findings. Nonalcoholic steatohepatitis (NASH) is a progressive subtype of NAFLD first defined by analogy to alcoholic hepatitis. Young children may have an alternate pattern of progressive NAFLD characterized by a zone 1 distribution of steatosis, inflammation, and fibrosis. Several grading and staging systems exist, but all require adequate biopsies. Although NASH generally shows fibrosis progression over time, some patients show regression of disease.