It could be Gilbert's Syndrome.
"Gilbert's syndrome, pronounced 'Jeel-Bears', often shortened to GS, is the most common hereditary cause of increased bilirubin, and is found in up to 5% of the population (though some gastroenterologists maintain that it is closer to 10%). The main symptom is otherwise harmless jaundice which does not require treatment, caused by elevated levels of unconjugated bilirubin in the bloodstream (hyperbilirubinemia).
The source of this hyperbilirubinemia is reduced activity of the enzyme glucuronyltransferase which conjugates bilirubin and some other lipophilic molecules. Conjugation renders the bilirubin water-soluble, after which it is excreted in bile into the duodenum....."