Fatty liver in a non-obese patient

A 15-year-old male with a body mass index of 19.5 kg/m2 (25th percentile) presented with asymptomatic elevated liver enzymes found on routine bloodwork; alanine transaminase was 98 U/L (upper normal limit: 55 U/L) and aspartate transaminase was 52 U/L (upper normal limit: 50 U/L). Complete blood count was normal without acanthocytes. Physical examination was normal except for an enlarged thyroid gland. There was no history of nausea, abdominal pain, diarrhea, systemic complaints or neurological symptoms. He denied alcohol intake or recreational drug use and was on no medications. Repeat transaminase levels over a 4-month period persisted slightly elevated with normal gamma glutamyltransferase, alkaline phosphatase and bilirubin levels. Further investigations for underlying liver disease including Wilson’s disease, autoimmune hepatitis, viral aetiologies and alpha-1 antitrypsin deficiency were negative. A liver ultrasound demonstrated coarse echogenicity without focal lesions, consistent with fatty infiltration. MRI suggested fatty liver without biliary duct pathology. A liver biopsy revealed nonalcoholic steatohepatitis (NASH) with fibrosis and early cirrhosis. Further investigations suggested the underlying diagnosis.