hepatic and biliary disorders
Metabolic Dysfunction–Associated Liver Disease (MASLD)
Introduction
Steatotic liver disease is due to excessive accumulation of lipid in hepatocytes. Metabolic dysfunction–associated liver disease (MASLD) includes simple fatty infiltration (a benign condition called steatotic liver disease), whereas metabolic dysfunction–associated steatohepatitis (MASH) is defined as the presence of fat leading to lipotoxicity and inflammatory damage to hepatocytes. Histologically, MASH is difficult to distinguish from alcoholic hepatitis. Thus to diagnose MASH, underlying alcohol use must be ruled out. Differentiating simple steatosis from MASH can be difficult without a liver biopsy, and elevated liver enzymes are not a sensitive predictor for identifying MASH. The presence of metabolic syndrome (obesity, dyslipidemia, hypertension, and glucose intolerance) increases the likelihood that a patient has MASH rather than simple steatosis. Pathogenesis is poorly understood but seems to be linked toinsulinresistance (eg, as in obesity or metabolic syndrome). Most patients are asymptomatic. Although noninvasive diagnostic tests are usually sufficient, liver biopsy remains the gold standard. Treatment includes elimination of causes and risk factors; new therapies are rapidly emerging but still in the clinical trial phase. (See also the American Association for the Study of Liver Diseases [AASLD]2018 practice guidanceon the diagnosis and management of MASLD.) MASLD includes simple fatty infiltration (a benign condition called steatotic liver disease) and metabolic dysfunction–associated steatohepatitis (MASH), a less common but more important variant. MASH (sometimes called steatonecrosis) is diagnosed most often in patients between 40 and 60 years but can occur in all age groups. Many affected patients have obesity, type 2 diabetes mellitus (or glucose intolerance), dyslipidemia, and/or metabolic syndrome. 