A 48-year-old woman has a 3-week history of fatigue as well as yellow skin and sclerae. Physical examination is unremarkable except for mild jaundice. The serum bilirubin level is 3.7 mg/dL, mostly in the unconjugated form. Liver function tests including serum AST, ALT, and alkaline phosphatase are normal. The hemoglobin level is 6.0 g/dL. After coicosteroids are administered, the jaundice resolves. Which of the following diseases is the most likely cause of hyperbilirubinemia in this patient?