The case report describes a progressive familial intrahepatic cholestasis II type Byler's syndrome with structural abnormality of the bile canalicular membrane. A child with a rare hereditary pathology,who is on the waiting list for liver transplantation, on the background of complex treatment, including diet therapy, drug therapy achieved a positive dynamics of clinical and laboratory parameters, acceleration of physical, psychomotor and intellectual development, that in general has improved the surgery prognosis and quality of life of the patient.