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Key Clinical Updates in Nonalcoholic Fatty Liver Disease
Noninvasive approaches to the assessment of fibrosis are now preferred, with liver biopsy reserved when results of noninvasive testing are inconclusive. The FIB-4 score is often used particularly to exclude advanced fibrosis because of its simplicity. It is based on age, platelet count, and serum AST and ALT levels.
Younossi ZM et al. Am J Gastroenterol. [PMID: 33284184]
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ESSENTIALS OF DIAGNOSIS
Often asymptomatic.
Elevated aminotransferase levels, hepatomegaly, or steatosis on ultrasonography.
Predominantly macrovesicular steatosis with or without inflammation and fibrosis on liver biopsy.
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GENERAL CONSIDERATIONS
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NAFLD is estimated to affect 37% of the US adult population and has increased in incidence at least fivefold since the late 1990s. Even adolescents and young adults may be affected. The principal causes of NAFLD are obesity (present in 40% or more of affected patients), diabetes mellitus (in 20% or more), and hypertriglyceridemia (in 20% or more) in association with insulin resistance as part of the metabolic syndrome. In fact, the alternative designation “metabolic-associated (or metabolic dysfunction‒associated) fatty liver disease” (MAFLD) has been proposed. The risk of NAFLD in persons with metabolic syndrome is 4 to 11 times higher than that of persons without insulin resistance. Nonobese persons (more frequently Asians) account for 10–20% of persons with NAFLD and have metabolic profiles characteristic of insulin resistance. Maternal obesity and higher maternal early-pregnancy glucose concentrations in mothers of European ancestry are associated with NAFLD in offspring, and breastfeeding for longer than 6 months with avoidance of early supplemental milk formula appears to reduce the risk of NAFLD in offspring during adolescence and in the mother later in life. Other causes of fatty liver include corticosteroids, amiodarone, diltiazem, methotrexate, tamoxifen, irinotecan, oxaliplatin, antiretroviral therapy, toxins (vinyl chloride, carbon tetrachloride, yellow phosphorus), endocrinopathies such as Cushing syndrome and hypopituitarism, polycystic ovary syndrome, hypothyroidism, hypobetalipoproteinemia and other metabolic disorders, obstructive sleep apnea (with chronic intermittent hypoxia), excessive dietary fructose consumption, malnutrition, starvation and refeeding syndrome, and total parenteral nutrition. NAFLD may be a predisposing factor in liver injury caused by some drugs. Gut dysbiosis, altered bile acid metabolism, and genetic factors (in up to 35% or patients), including polymorphisms of the gene that encodes apolipoprotein C3, are thought to play a role in NAFLD (and likely account for NAFLD in lean persons), and polymorphisms of the patatin-like phospholipase domain-containing 3 (PNPLA3) gene modify the natural history of NAFLD and may account in part for an increased risk in Latinx persons. A polymorphism of TM6SF2 is associated with advanced fibrosis and cirrhosis, and a polymorphism of HSD17B13 is associated with a reduced risk of progression of steatosis to steatohepatitis and of chronic liver disease. Other associations include variants of MBOAT1 and GCKR. The risk of NAFLD is increased in persons with psoriasis and appears to correlate with the activity of psoriasis. Soft drink consumption and cholecystectomy have been reported to be associated ...