Secondary causes of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is becoming the most common cause of chronic liver disease in the developing world, found in 17-30% of the population in Western countries and 2-4% worldwide. Defined as the accumulation of fatty acid content greater than 5% of liver weight, NAFLD is a spectrum of disease ranging from simple steatosis to nonalcoholic steatohepatitis. The pathophysiology of NAFLD involves increased de novo synthesis of fatty acids in hepatocytes, the retention of lipids due to impaired hepatocyte apolipoprotein secretion or beta-oxidation. The well-known primary causes of NAFLD are obesity, type II diabetes, dyslipidemia, and insulin resistance. However, other less common conditions can cause a similar clinical and histologic picture, and should be considered in patients who present with NAFLD but do not have traditional risk factors. In this review, we discuss uncommon but important causes of NAFLD, including inborn errors of metabolism, iatrogenic causes, viral hepatitis, and nutritional disorders to provide practicing clinicians with an understanding of the less well recognized causes of NAFLD.