NAFLD Pediatric Database 2

Inclusion Criteria: * Continuing participants: * Previously enrolled in the NAFLD Database study or TONIC trial * Age at least 2 years and not older than 17 years during the consent process * Willingness to continue to be followed for up to 4 years * Ability and willingness to give written, informed parental consent and child assent, per local IRB guidelines, to be enrolled into the pediatric Database 2 study * New participants: * Age at least 2 years of age and not older than 17 years during the consent process * Willingness to be followed for up to 4 years * Ability and willingness to give written, informed parent consent and child assent to be enrolled into the pediatric Database 2 study * Minimal or no alcohol use history consistent with NAFLD * Having undergone a liver biopsy that is obtained within 120 days of enrollment * Collection of biosamples (serum, plasma, DNA, and, if available, liver tissue) within 90 days prior to enrollment and 0-90 days before or 4-90 days after the standard of care liver biopsy Exclusion Criteria: * Total parenteral nutrition for more than 1 month within a 6 month period before baseline liver biopsy * Short bowel syndrome * History of gastric or jejunoileal bypass preceding the diagnosis of NAFLD. Bariatric surgery performed following enrollment is not exclusionary. Liver biopsies obtained during bariatric surgery cannot be used for enrollment because of the associated surgical or anesthetic acute changes and the weight loss efforts that precede bariatric surgery * History of biliopancreatic diversion * Evidence of advanced liver disease defined as a Child-Pugh-Turcotte score equal to or greater than 10 * Evidence of chronic hepatitis B as marked by the presence of HBsAg in serum (participants with isolated antibody to hepatitis B core antigen, anti-HBc total, are not excluded) * Evidence of chronic hepatitis C as marked by the presence of anti-HCV or HCV RNA in serum * Low alpha-1-antitrypsin level and ZZ phenotype (both determined at the discretion of the investigator) * Wilson's disease * Known glycogen storage disease * Known dysbetalipoproteinemia * Known phenotypic hemochromatosis (HII greater than 1.9 or removal of more than 4 g of iron by phlebotomy) * Prominent bile duct injury (florid duct lesions or periductal sclerosis) or bile duct paucity * Chronic cholestasis * Vascular lesions (vasculitis, cardiac sclerosis, acute or chronic Budd-Chiari, hepatoportal sclerosis, peliosis) * Iron overload greater than 3+ * Zones of confluent necrosis, infarction, massive or sub-massive, pan-acinar necrosis * Multiple epithelioid granulomas * Congenital hepatic fibrosis * Cystic fibrosis * Polycystic liver disease * Other metabolic or congenital liver disease * Evidence of systemic infectious disease * Known HIV positive * Disseminated or advanced malignancy * Concomitant severe underlying systemic illness that in the opinion of the investigator would interfere with completion of follow-up * Active drug use or dependence that, in the opinion of the study investigator, would interfere with adherence to study requirements * Any other condition, which in the opinion of the investigator would impede compliance or hinder completion of study * Inability for parent to provide informed consent and child 8 years or greater to give assent