MASLD in Special Populations

Pediatric nonalcoholic fatty liver disease (NAFLD) presents as persistent hepatic steatosis in individuals aged 18 years or younger, distinct from genetic or metabolic disorders, infections, steatogenic medications, alcohol use, or malnutrition. NAFLD ranges from simple steatosis to nonalcoholic steatohepatitis (NASH), an inflammatory and progressive form advancing to NAFLD cirrhosis, becoming a significant cause of chronic liver disease in both children and adults [1, 2]. Although only 3–5% of NAFLD patients develop significant liver disease, it is anticipated to become the primary indication for liver transplantation in adults in the future [3]. Formerly considered an adult ailment, these liver disorders are increasingly prevalent among children, necessitating a thorough understanding of their epidemiology, etiology, clinical manifestations, and management. The terminology for NAFLD has evolved, with the introduction of metabolic-associated fatty liver disease (MAFLD) to encompass the intricate connection between metabolic dysfunction, obesity, and liver pathology [4]. Recently, various societies have proposed replacing NAFLD with metabolic dysfunction-associated steatotic liver disease (MASLD), defined by the presence of at least one of five cardiometabolic risk factors, with the need to rule out alternative causes of hepatic steatosis and identify coexisting conditions [5]. This evolving nomenclature underscores the complex relationship between metabolic disturbances and hepatic lipid accumulation. However, the introduction of the terms MASLD has primarily targeted adult patients, potentially leading to ambiguity, especially regarding the metabolic aspect. Adult hepatologists, focusing on steatosis and insulin resistance mechanisms, may interpret the metabolic term differently than pediatric hepatologists, who prioritize considering inborn errors of metabolism in younger children with fatty liver disease. To maintain clarity and avoid potential issues arising from different interpretations, this chapter will use the terminology MASLD unless referencing existing literature.