Jaundice, the yellowing of the skin and eyes, is a sign that bilirubin is building up in the body, not a disease in itself. Many causes, such as hepatitis, gallstones or alcohol, aren’t inherited at all. But some people inherit genes that make their body handle bilirubin less efficiently, so jaundice can run in families.1PubMed Central. Gilbert’s Syndrome, Bilirubin Level and UGT1A1∗28 Genotype in Men of North-West Region of Russia The most common inherited form is so mild and widespread that many carriers never learn they have it, while the serious forms are rare and usually show up in babies.
How Genes Affect Bilirubin
Bilirubin is a yellow substance made when old red blood cells are broken down.2MedlinePlus Genetics. UGT1A1 gene In the liver, a single enzyme made from the UGT1A1 gene converts it into a form that dissolves and can leave the body.3MedlinePlus Genetics. UGT1A1 gene The processed bilirubin is then pumped into bile by other liver proteins, each made from its own gene.4PubMed. A common Dubin-Johnson syndrome mutation impairs protein maturation and transport activity of MRP2 (ABCC2) So inherited jaundice can come from too much bilirubin being made, too little being processed, or processed bilirubin not leaving the liver.
Blood tests split bilirubin into two kinds: unprocessed (also called indirect or unconjugated) and processed (direct or conjugated). High unprocessed bilirubin points to red cell breakdown or a processing problem.5Journal of Clinical and Translational Hepatology. Expert Consensus on the Diagnosis and Management of Inherited Hyperbilirubinemia High processed bilirubin points to a problem getting it out of the liver.6PubMed. A common Dubin-Johnson syndrome mutation impairs protein maturation and transport activity of MRP2 (ABCC2)
Many of these conditions need a faulty copy of a gene from both parents. Parents who each carry one copy are usually healthy themselves, which is why a condition can appear in a child with no family history at all.
Gilbert Syndrome, the Most Common Inherited Cause
Gilbert syndrome affects about 10% of people worldwide.7PubMed Central. Gilbert’s Syndrome, Bilirubin Level and UGT1A1∗28 Genotype in Men of North-West Region of Russia Most people with it have an extra repeat in the switch region of the UGT1A1 gene, which sharply lowers the enzyme’s activity.8PubMed Central. Gilbert’s Syndrome, Bilirubin Level and UGT1A1∗28 Genotype in Men of North-West Region of Russia That variant alone may not be enough, though, and other small variations in the same gene seem to add up to cause the condition.9PubMed Central. Combined effect of regulatory polymorphisms on transcription of UGT1A1 as a cause of Gilbert syndrome
It is most often tied to having two copies of the common variant, one from each parent, and it often shows up in several relatives. Many who inherit it never notice anything. Men usually show higher bilirubin than women with the same variant, so it is picked up more often in men.
A flare typically means yellow eyes during fasting, illness, stress, hard exercise or poor sleep. It fades on its own within days once the trigger passes. Some people notice tiredness, though it’s unclear whether bilirubin causes it. No treatment is needed.
Blood counts are typically normal, which helps doctors tell Gilbert syndrome apart from red blood cell disorders.10Journal of Clinical and Translational Hepatology. Expert Consensus on the Diagnosis and Management of Inherited Hyperbilirubinemia Bilirubin is also a strong antioxidant,11PubMed. Induction of Mild Hyperbilirubinemia: Hype or Real Therapeutic Opportunity? and some studies suggest people with Gilbert syndrome may have a lower risk of heart disease than average.12PubMed Central. Gilbert’s syndrome: The good, the bad and the ugly The trade-off is that higher bilirubin raises the chance of gallstones, found in about 9% of people with Gilbert syndrome in one large group.13PubMed Central. Incidence and Risk of Gallstone Disease in Gilbert’s Syndrome Patients in Indian Population
Diagnosis usually rests on repeated, mildly high indirect bilirubin with normal liver tests. It is often found by chance on a routine test. A genetic test can confirm it but often isn’t needed.
Because the same enzyme clears some drugs, a few medicines can build up or raise bilirubin. The cancer drug irinotecan is the best-known example, so tell doctors you have Gilbert syndrome before any new treatment.
Bilirubin in Gilbert syndrome rises and falls from one test to the next, so a normal result on one day doesn’t rule it out. The condition does not damage the liver or lead to cirrhosis or liver failure.
Rarer Inherited Bilirubin Disorders
Faults in the same UGT1A1 gene that cause Gilbert syndrome can, when severe, cause Crigler-Najjar syndrome.14Human Mutation. Genetic lesions of bilirubin uridine-diphosphoglucuronate glucuronosyltransferase (UGT1A1) causing Crigler-Najjar and Gilbert syndromes: Correlation of genotype to phenotype Type 1 has no working enzyme and type 2 has partial activity.15PubMed. Spectrum of UGT1A1 mutations in Crigler-Najjar (CN) syndrome patients: identification of twelve novel alleles and genotype-phenotype correlation Type 1 causes very high bilirubin from birth that can damage the brain if untreated.16Human Mutation. Genetic lesions of bilirubin uridine-diphosphoglucuronate glucuronosyltransferase (UGT1A1) causing Crigler-Najjar and Gilbert syndromes: Correlation of genotype to phenotype Both parents must pass on a faulty copy.17Human Mutation. Genetic lesions of bilirubin uridine-diphosphoglucuronate glucuronosyltransferase (UGT1A1) causing Crigler-Najjar and Gilbert syndromes: Correlation of genotype to phenotype
In practice, type 1 usually shows up within days of birth as deep jaundice that doesn’t fade the way ordinary newborn jaundice does. Type 2 is milder and may not be noticed until later in childhood or even adulthood, with lower bilirubin that is less likely to injure the brain. Many people with type 2 do well on phenobarbital, a medicine that boosts the little enzyme activity they have. Type 1 doesn’t respond, because there is no working enzyme to boost. Even in type 2, illness or fasting can push bilirubin up, so people with it are told to seek care when they are unwell.
In Dubin-Johnson syndrome, a missing pump (MRP2) traps processed bilirubin in the liver.18PubMed. A common Dubin-Johnson syndrome mutation impairs protein maturation and transport activity of MRP2 (ABCC2) It needs faulty copies of the ABCC2 gene from both parents.19BMJ Open. ABCC2 p.R393W variant contributes to Dubin-Johnson syndrome by targeting MRP2 to proteasome degradation Rotor syndrome happens when two liver uptake proteins both fail, from faults in two genes.20PubMed. Complete OATP1B1 and OATP1B3 deficiency causes human Rotor syndrome by interrupting conjugated bilirubin reuptake into the liver It is benign and causes only mild jaundice.21PubMed. SLCO1B1 and SLCO1B3 genetic mutations in Taiwanese patients with Rotor syndrome
Some signs suggest something other than Gilbert syndrome: jaundice that is deep or constant rather than occasional, or very high bilirubin in a newborn that lasts beyond the first weeks. High direct bilirubin calls for further tests.
Inherited Liver Diseases That Cause Jaundice
Faults in genes for liver pump proteins range from benign conditions to progressive familial intrahepatic cholestasis, which blocks bile flow in children.22PubMed Central. ATP-binding Cassette Transporter Defects and Their Roles in Hepatic Diseases In alpha-1 antitrypsin deficiency, two copies of the Z variant can cause both lung and liver disease.23PubMed Central. Alpha-1 Antitrypsin Deficiency-Mediated Liver Toxicity: Why Do Some Patients Do Poorly? What Do We Know So Far? Its liver effects vary widely, from passing newborn jaundice to cirrhosis later.24PubMed Central. Alpha-1 Antitrypsin Deficiency-Mediated Liver Toxicity: Why Do Some Patients Do Poorly? What Do We Know So Far? In Wilson disease, faults in the ATP7B gene let copper build up in the liver and brain.25PubMed Central. A review and current perspective on Wilson disease It can range from no symptoms to liver failure, mood or movement problems, and red cell breakdown.26PubMed Central. A review and current perspective on Wilson disease Here jaundice signals real liver injury, unlike the bilirubin-only conditions above, and liver tests beyond bilirubin are abnormal.
In progressive familial intrahepatic cholestasis, inherited faults in bile pumps mean bile can’t leave the liver properly, so it builds up and injures liver cells. Intense itching is often an early and distressing sign in affected children, sometimes appearing before jaundice is obvious. Children can grow poorly, because bile is needed to absorb fat and fat-soluble vitamins from food. Treatment ranges from medicines that ease bile flow and itching to surgery or liver transplant when the disease progresses.
Early diagnosis matters because Wilson disease is treatable with medicines that remove copper, and family members of someone with it should be tested. People with alpha-1 antitrypsin deficiency should avoid smoking and limit alcohol.
Inherited Blood Disorders That Cause Jaundice
G6PD deficiency, common worldwide, makes red cells fragile under stress.27PubMed Central. Glucose-6-Phosphate Dehydrogenase Deficiency and Neonatal Hyperbilirubinemia: Insights on Pathophysiology, Diagnosis, and Gene Variants in Disease Heterogeneity Certain triggers like fava beans can then cause sudden red cell breakdown.28PubMed Central. Glucose-6-Phosphate Dehydrogenase Deficiency and Neonatal Hyperbilirubinemia: Insights on Pathophysiology, Diagnosis, and Gene Variants in Disease Heterogeneity Breakdown typically begins within a day or a few days of exposure to a trigger, with fatigue, yellow eyes and dark urine. In hereditary spherocytosis, faulty membrane genes make red cells round and stiff, so they break down early.29PubMed Central. De novo mutations in ANK1 and SPTB cause hereditary spherocytosis: three case reports and literature review In spherocytosis the spleen may also be enlarged. These conditions cause jaundice along with anaemia, unlike Gilbert syndrome.30Journal of Clinical and Translational Hepatology. Expert Consensus on the Diagnosis and Management of Inherited Hyperbilirubinemia
Most of the time people with G6PD deficiency feel completely well. Most episodes settle by themselves once the trigger is removed, though severe ones need hospital care and sometimes a transfusion. The effect depends on the variant, so some people are only mildly affected while others react strongly to the same trigger.
Living with it means avoiding fava beans and mothballs containing naphthalene, and carrying a list of drugs to avoid, since some medicines can trigger breakdown too. It is passed through the X chromosome, so it is more common and usually more severe in boys, though girls can be affected too.
Newborn Jaundice and Family Genes
Before birth, the mother’s body clears the baby’s bilirubin. After birth the baby’s own liver enzyme is still immature, so most newborns have some rise in bilirubin. Gene variants that weaken the enzyme or the liver’s uptake proteins stack on top of this immaturity, which is why they matter most in the first days. Breastfed babies who aren’t feeding well can lose fluid and clear less bilirubin through stool, so poor feeding can worsen jaundice on top of genetic risk.
Variants in G6PD, UGT1A1 and SLCO1B1 can combine with each other and with other factors to raise a baby’s bilirubin.31PubMed. Exploring the genetic architecture of neonatal hyperbilirubinemia G6PD-deficient babies have a much higher risk of newborn jaundice, usually starting on day 2 or 3.32Haematologica. Glucose 6-phosphate dehydrogenase deficiency: from genotype to phenotype Jaundice can be severe with prematurity, infection or mothballs in bedding, and very high levels can cause brain damage called kernicterus.33Haematologica. Glucose 6-phosphate dehydrogenase deficiency: from genotype to phenotype
Normal newborn jaundice appears after day 1 and fades in 1 to 2 weeks. Jaundice in the first 24 hours needs urgent checking, as does jaundice past 2 weeks, pale stools or dark urine.
If the family has a history, tell the midwife or doctor about G6PD deficiency, spherocytosis or Gilbert syndrome, and ask whether the baby should have a G6PD test. Keep mothballs away from baby clothes and bedding. Seek care fast if yellowing spreads down the body, or if the baby feeds poorly or is unusually sleepy.
A skin scanner or a heel-prick blood test measures the baby’s bilirubin, and the result is compared with charts that account for age in hours. Phototherapy, in which the baby lies under special blue light, is the standard treatment and breaks bilirubin into forms that can be passed out of the body. In rare severe cases a blood exchange transfusion lowers bilirubin quickly. Babies with known risk factors, such as a G6PD-deficient relative or a blood-group mismatch, are often checked more closely and sooner.
Testing for an Inherited Cause
Doctors first compare processed and unprocessed bilirubin and check blood counts.34Journal of Clinical and Translational Hepatology. Expert Consensus on the Diagnosis and Management of Inherited Hyperbilirubinemia A full blood count and a look at the red cells under the microscope help separate red cell disorders from liver-processing problems. A reticulocyte count, which measures young red cells, shows whether the bone marrow is replacing cells lost to breakdown. A direct antiglobulin test checks whether antibodies are attacking the red cells, which would point to an immune cause rather than an inherited one.
When the cause stays unclear, gene panel testing can check many jaundice genes at once. In one group of children with high unprocessed bilirubin, testing found a genetic cause in 4 of 10 tested.35PubMed Central. Diagnostic Utility of Next-Generation Sequencing for Unconjugated Hyperbilirubinemia in Children The most common findings were Gilbert syndrome and hereditary spherocytosis.36PubMed Central. Diagnostic Utility of Next-Generation Sequencing for Unconjugated Hyperbilirubinemia in Children
Genetic testing is worth it for severe or unexplained jaundice in a child, or when planning a family in which a serious condition runs. It is usually unnecessary for typical Gilbert syndrome.
For the appointment, bring your family history of jaundice, anaemia, gallstones or liver disease, notes on when yellowing appears and what seems to trigger it, and any previous bilirubin results.
Treatment Options for Inherited Jaundice
Gilbert, Dubin-Johnson and Rotor syndromes usually need no treatment. Crigler-Najjar type 1 is different: it needs many hours of daily light therapy, and a liver transplant has been the main cure.37Preprints. Therapeutic Options for Crigler-Najjar Syndrome: A Scoping Review Light therapy uses blue-green light on the skin to turn bilirubin into forms that dissolve and can be passed out without the missing enzyme. Because the time under the lamp has to be long, it is usually done at home each day, often overnight, and it takes a real toll on family routines. It becomes less effective as a child grows, because skin thickens and surface area shrinks relative to body size, which is one reason transplant is considered.
In an early gene therapy trial, people on the higher dose kept bilirubin below dangerous levels without light therapy for over a year and a half.38PubMed. Gene Therapy in Patients with the Crigler-Najjar Syndrome Gene therapy is harder in children because the liver grows and some already have immunity to the virus carrier.39Preprints. Therapeutic Options for Crigler-Najjar Syndrome: A Scoping Review
For mild inherited jaundice, eat regularly and avoid long fasts, stay hydrated and rest during illness, and get any gallbladder pain checked. Variants in bilirubin genes raise the risk of jaundice from certain drugs, so tell doctors about any inherited bilirubin condition, and report new yellowing after starting a medicine.