GS was first identified by the French doctors Nicolas Augustin Gilbert (after whom it is named) and Pierre Lereboullet in 1900. They described a syndrome of benign, periodic but chronic jaundice occurring without any other symptoms of liver disease.
Today, GS is relatively common. It is thought to affect about one person in 20 or about 4% of the population. Some estimates are higher. It affects both males and females.
GS is thought to be hereditary, meaning that it is caused by a gene that runs in your family.
Genes contain the instructions for making up your body. GS is caused by a variant gene that has a ‘mutation’. A mutation is a permanent change in the code of the DNA making up a gene or chromosome. This can alter the way a physical characteristic is expressed or cause some function in the body to occur differently. Sometimes the word ‘variant’ is used instead of mutation as many changes do not cause any disorder.
In GS the mutation causes ‘reduced gene expression’, meaning that it limits production of thespecific UGT enzyme (called UGT1A1) responsible for conjugating bilirubin.
This mutation has been pinpointed to occur on a gene called the UDP-glucoronosyltransferase gene. Half the general population may have this gene.
However, GS is a ‘recessive’ disorder, meaning that you need to have two copies of the abnormal gene (one from each parent) to acquire it. People who inherit the same mutated gene from both their parents are termed ‘homozygote’. Even so, having two abnormal genes does not necessarily mean that you will go on to develop GS.
Although it is not understood why, some people with only a single abnormal gene (‘heterozygotes’) have higher than usual levels of unconjugated bilirubin but do not have GS.
At present there is no established genetic test for GS.