Adult-onset Still's disease (AOSD) is a systemic inflammatory disorder of unknown etiology that usually affects young adults. 1 Spiking fever, arthritis, and evanescent rash are commonly observed during the course of the disease. Other frequently observed clinical features include sore throat, hepatosplenomegaly, lymphadenopathy, and serositis. 2 Adult-onset Still's disease is usually complicated by liver dysfunction. 3 However, cases of autoimmune hepatitis (AIH) complicated by AOSD are rare, and discerning the cause of liver dysfunction as AOSD or AIH is difficult. This was a very rare case that could be followed up from acute onset to recurrence of AIH complicated by AOSD. Herein, we report a case of AIH complicated by AOSD that was successfully diagnosed by a liver biopsy.

Differentiating autoimmune hepatitis from liver dysfunction due to adult-onset Still’s disease is important in deciding whether to terminate or continue corticosteroid therapy, and also in terms of management of cirrhosis and surveillance of hepatocellular carcinoma. Liver biopsy is thought to be the most important determinant for differential diagnosis.

Plexiform neurofibromas (PNs) occur in approximately 50% of patients with neurofibromatosis type 1 (NF 1). PNs are rare in the abdominal cavity and especially rare in hepatobiliary lesions. A 31-year-old man with NF1 had a tumor extending along the celiac artery, superior mesenteric artery, and intrahepatic portal vein. We diagnosed him with diffuse PN based on liver tumor biopsy findings and the tumor form. Because the tumor had invaded along the intrahepatic portal vein, surgical resection was deemed difficult, and the patient was followed up with imaging studies. The patient remained asymptomatic without tumor growth.