Special Population: Lean MASH.

Metabolic dysfunction-associated steatotic liver disease in lean individuals represents a distinct phenotype affecting approximately 5.1% of the global population, characterized by hepatic steatosis with cardiometabolic risk factors despite a normal body mass index. This condition demonstrates unique pathogenic mechanisms, including genetic predisposition, visceral adiposity, and metabolic dysregulation. Prevalence varies globally, with initial recognition in Asian populations, but occurs across diverse ethnicities. Diagnosis relies on imaging modalities and exclusion of secondary causes. Management emphasizes lifestyle interventions targeting 3% to 5% weight reduction. Limited pharmacological data exist, as most clinical trials exclude lean patients. Understanding this population is crucial.