- Incidence: 500.00 cases per 100,000 person-years
- Peak incidence: 20-30 years
- Sex ratio: 1:1
- unconjugated hyperbilirubinaemia (i.e. not in urine)
- jaundice may only be seen during an intercurrent illness, exercise or fasting
Provocative testing with IV nicotinic acid may sometimes be used to investigate certain cases.