A 16 y.o. teenager complains of weakness, dizziness, sense of heaviness in the left hypochondrium. Objectively: skin and visible mucous membranes are icteric. Steeple skull. Liver 2 cm, the lower pole of spleen is at the level of navel. Blood test: RBC- 2,7 × 1012/l, Hb- 88 g/L, WBC-5,6 × 109/l, ESR - 15 mm/h. What is the most probable reason of bilirubin level change?