Introduction: Acute hepatitis is always a diagnostic challenge. In the setting of a young adult with type 1 diabetes mellitus (T1DM), the differential diagnosis usually includes viral hepatitis, autoimmune, and metabolic liver diseases such as juvenile hemochromatosis. Liver biopsy (LB) may have a key role in establishing the correct diagnosis. Case Report: A female patient, 29 years old, presented with a 2-month history of asthenia, anorexia, peripheral edema, and epigastric pain, more intense in the last 2 weeks. The patient had poorly controlled T1DM (HbA1c 10.9%, normal range 4-6) diagnosed at the age of 4. She denied the use of drugs, except sporadic alcohol intake and Indian tobacco smoking 6 months before. Physical examination revealed hepatomegaly and peripheral edema without jaundice or altered consciousness. Laboratory analysis revealed acute hepatitis with increased aspartate aminotransferase (991 U/L, normal <31), alanine aminotransferase (461 U/L, normal <31), gamma-glutamyl transferase (219 U/L, normal <31), and alkaline phosphatase (172 U/l, normal <120). Bilirubin levels were normal, the patient had albumin deficiency (28.8 g/L, normal range 38-51) without coagulopathy. The ultrasound confirmed hepatomegaly without nodules or signs of portal hypertension. The etiologic study was negative for viral markers, autoimmunity, iron parameters, and manifestations of Wilson’s disease. LB was performed and the histological examination detected preserved architecture, ballooning, and universal clarification of hepatocytes and cell membrane accentuation with “mosaic” pattern distribution (typically seen in the Mauriac syndrome); glycogenated nuclei were also present. During hospitalization, there was a clinical and analytical improvement associated with glycemic control after adjustment and compliance with nutrition and insulin therapy regimens. At follow-up visit, after 3 months, all hepatic laboratory abnormalities and hepatomegaly had resolved. Discussion: The glycogenic hepatopathy (GH) is a rare cause of elevated aminotransferases in T1DM, being more frequent in patients with poor glycemic control. A similar condition was described by Mauriac, characterized by delayed growth and puberty, hepatomegaly, and cushingoid appearance. The authors intend to raise awareness to the diagnostic challenge of hepatitis in diabetic patients by reporting a case of clinically resolved GH. Disclosure - Helder Cardoso - Advisory committee: Abbvie, Janssen; Speaking and Teaching: BMS, Bayer, Roche.