Two cases of chronic unconjugated hyperbilirubinemia and marked retention of indocyanine green (ICG) are described. Since bilirubin uridine diphosphate (UDP)-glucuronyl transferase activities were depressed in their liver, the patients seemed to have bilirubin metabolism similar to that in Gilbert's syndrome. However, the ICG fractional disappearance rates of the cases were rather low (0.018 and 0.019) compared to the rates reported for Gilbert's syndrome. These results suggest that the patients had a new metabolic disorder which results in constitutional unconjugated hyperbilirubinemia and ICG intolerance.</p
