Tom is a 25 year old office worker who has a free occupational health screen at work which was normal except for some abnormalities in some of his screening blood tests. He attends the GP surgery with a copy of the results which are all normal except a slightly raised bilirubin of 31. There are no previous results on his medical record, and he has no past medical history of note and is otherwise well.
Based on the history alone, what is his most likely diagnosis?
