Dual etiology vs. MetALD: how MAFLD and MASLD address liver diseases coexistence

Fatty liver disease associated with metabolic dysfunction has emerged as a significant global health challenge. This condition often coexists with other liver diseases, such as alcohol-related liver disease and viral hepatitis, complicating both diagnosis and management. To address the limitations of the non-alcoholic fatty liver disease (NAFLD) classification, two alternative frameworks have been proposed: metabolic dysfunction-associated fatty liver disease (MAFLD) in 2020 and metabolic dysfunction-associated steatotic liver disease (MASLD) in 2023. A key difference between these definitions is how they consider fatty liver disease in relation to the coexistence of other liver conditions. MAFLD adopts a dual etiology concept, creating a unified classification system that aligns with contemporary clinical and epidemiological needs. In contrast, MASLD introduces a new term, MetALD (metabolic and alcohol-related/associated liver disease), to describe patients who have both metabolic dysfunction and excessive alcohol intake. This review critically examines the clinical, research, and epidemiological implications of the differing approaches of MAFLD and MASLD, offering insights into their potential to enhance the understanding and management of multi-etiology liver diseases.