Genetic polymorphisms in Thai neonates with hyperbilirubinemia

Serum microRNAs as new biomarkers for detecting subclinical hemolysis in the nonacute phase of G6PD deficiency

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is one of the most common enzymopathies worldwide. Patients with G6PD deficiency are usually asymptomatic throughout their life but can develop acute hemolysis after exposure to free radicals or certain medications. Several studies have shown that serum miRNAs can be used as prognostic biomarkers in various types of hemolytic anemias. However, the impact of G6PD deficiency on circulating miRNA profiles is largely unknown. The present study aimed to assess the use of serum miRNAs as biomarkers for detecting hemolysis in the nonacute phase of G6PD deficiency. Patients with severe or moderate G6PD Viangchan (871G > A) deficiency and normal G6PD patients were enrolled in the present study. The biochemical hemolysis indices were normal in the three groups, while the levels of serum miR-451a, miR-16, and miR-155 were significantly increased in patients with severe G6PD deficiency. In addition, 3D analysis of a set of three miRNAs (miR-451a, miR-16, and miR-155) was able to differentiate G6PD-deficient individuals from healthy individuals, suggesting that these three miRNAs may serve as potential biomarkers for patients in the nonhemolytic phase of G6PD deficiency. In conclusion, miRNAs can be utilized as additional biomarkers to detect hemolysis in the nonacute phase of G6PD deficiency.

Effect of neonatal reticulocytosis on glucose 6-phosphate dehydrogenase (G6PD) activity and G6PD deficiency detection: a cross-sectional study

BACKGROUND

Screening for G6PD deficiency in newborns can help prevent severe hemolysis, hyperbilirubinemia, and bilirubin encephalopathy, as recommended by the World Health Organization (WHO). It has been speculated that the presence of a high number of reticulocytes in newborns interferes with the diagnosis of G6PD deficiency since reticulocytes contain higher amounts of G6PD enzyme than mature erythrocytes. Therefore, the purposes of this study were to assess the effect of reticulocytosis in the determination of blood G6PD activity in Thai newborns by using a novel automated UV-based enzymatic assay and to validate the performance of this assay for the detection of G6PD deficiency in newborn samples.

METHODS

The levels of reticulocytes and G6PD activity were measured in blood samples collected from 1,015 newborns. G6PD mutations were identified using TaqMan^® SNP genotyping assay, PCR-restriction fragment length polymorphism (PCR-RFLP), and direct sequencing. The correlation between the levels of reticulocytes and G6PD activity was examined. The performance of the automated method was compared with that of the fluorescent spot test (FST) and the standard quantitative assay.

RESULTS

The automated assay detected G6PD deficiency in 6.5% of the total newborn subjects compared to 5.3% and 6.1% by the FST and the standard method, respectively. The minor allele frequencies (MAFs) of G6PD Viangchan^G871A, G6PD Mahidol^G487A, and G6PD Union^C1360T were 0.066, 0.005, and 0.005, respectively. The reticulocyte counts in newborns with G6PD deficiency were significantly higher than those in normal male newborns (p < 0.001). Compared with normal newborns after controlling for thalassemias and hemoglobinopathies, G6PD-deficient patients with the G6PD Viangchan^G871A mutation exhibited elevated reticulocyte counts (5.82 ± 1.73%, p < 0.001). In a group of G6PD normal newborns, the percentage of reticulocytes was positively correlated with G6PD activity (r = 0.327, p < 0.001). However, there was no correlation between G6PD activity and the levels of reticulocytes in subjects with G6PD deficiency (r = -0.019, p = 0.881). The level of agreement in the detection of G6PD deficiency was 0.999, while the area under the receiver operating characteristic (AUC) curve demonstrated that the automated method had 98.4% sensitivity, 99.5% specificity, 92.4% positive predictive value (PPV), 99.9% negative predictive value (NPV), and 99.4% accuracy.

CONCLUSIONS

We report that reticulocytosis does not have a statistically significant effect on the detection of G6PD deficiency in newborns by both qualitative and quantitative methods.

Contribution of genetic factors to high rates of neonatal hyperbilirubinaemia on the Thailand-Myanmar border

Very high unconjugated bilirubin plasma concentrations in neonates (neonatal hyperbilirubinaemia; NH) may cause neurologic damage (kernicterus). Both increased red blood cell turn-over and immaturity of hepatic glucuronidation contribute to neonatal hyperbilirubinaemia. The incidence of NH requiring phototherapy during the first week of life on the Thailand-Myanmar border is high (approximately 25%). On the Thailand-Myanmar border we investigated the contribution of genetic risk factors to high bilirubin levels in the first month of life in 1596 neonates enrolled in a prospective observational birth cohort study. Lower gestational age (<38 weeks), mutations in the genes encoding glucose-6-phosphate dehydrogenase (G6PD) and uridine 5'-diphospho-glucuronosyltransferase (UGT) 1A1 were identified as the main independent risk factors for NH in the first week, and for prolonged jaundice in the first month of life. Population attributable risks (PAR%) were 61.7% for lower gestational age, 22.9% for hemi or homozygous and 9.9% for heterozygous G6PD deficiency respectively, and 6.3% for UGT1A1*6 homozygosity. In neonates with an estimated gestational age ≥ 38 weeks, G6PD mutations contributed PARs of 38.1% and 23.6% for "early" (≤ 48 hours) and "late" (49-168 hours) NH respectively. For late NH, the PAR for UGT1A1*6 homozygosity was 7.7%. Maternal excess weight was also a significant risk factor for "early" NH while maternal mutations on the beta-globin gene, prolonged rupture of membranes, large haematomas and neonatal sepsis were risk factors for "late" NH. For prolonged jaundice during the first month of life, G6PD mutations and UGT1A1*6 mutation, together with lower gestational age at birth and presence of haematoma were significant risk factors. In this population, genetic factors contribute considerably to the high risk of NH. Diagnostic tools to identify G6PD deficiency at birth would facilitate early recognition of high risk cases.

The relationship between hyperbilirubinemia and the promoter region and first exon of UGT1A1 gene polymorphisms in Vietnamese newborns

BACKGROUND

To investigate the relationship between unexplained indirect hyperbilirubinemia of Vietnamese newborns and the polymorphism of the promoter TATA box and exon 1 of bilirubin uridine diphosphate glucuronosyltransferase (UGT1A1) gene.

METHODS

A total of 149 neonates were divided into the hyperbilirubinemia group (n = 99) and control group (n = 50). The gene polymorphisms of UGT1A1 gene in the two groups were detected by PCR and direct sequencing, which revealed the relationship between UGT1A1 polymorphism with neonatal hyperbilirubinemia of neonates. The types of UGT1A1 polymorphism in the hyperbilirubinemia group and the peak total serum bilirubin (PSB) levels with different genotypes were observed.

RESULTS

(1) (TA)7 insertion mutation, 211G>A, 189C>T, 190G>A, 378C>T and 686C>A were detected. (2) The allele frequency of 211G>A allele mutation was significantly different between the two groups (p < 0.05). (3) Logistic regression analysis showed that homozygosity and heterozygosity of 211G>A were both significantly associated with neonatal hyperbilirubinemia. (4) In the hyperbilirubinemia group, the peak total serum bilirubin level of 211G>A homozygous neonates was higher than that of the wild-type neonates (p < 0.05).

CONCLUSIONS

We noted that there was an association between neonates with unexplained indirect hyperbilirubinemia in Vietnam and the polymorphism of UGT1A1c.211G>A. In addition, the homozygous 211G>A polymorphism was related to the degree of hyperbilirubinemia.

IMPACT

Our article provided data on UGT1A1 polymorphism distribution in the Vietnamese population, which have not been reported yet. Our findings revealed that mutations in UGT1A1 gene are risk factors for unexplained hyperbilirubinemia in Vietnamese neonates. Our article will strengthen the cognition of neonatal jaundice at the genetic level in the pediatric field in Vietnam.

SLCO1B1 c.388A > G variant incidence and the severity of hyperbilirubinemia in Indonesian neonates

OBJECTIVE

It has been established that genetic factors play a substantial role in the development of neonatal hyperbilirubinemia. The population of Indonesia and other Southeast Asian countries has similar, yet different genetic makeup compared to the rest of Asia. Aside from UGT1A1, variants of SLCO1B1 have also been known to contribute to the severity of neonatal hyperbilirubinemia in Asian populations. Since there has been no report on SLCO1B1 polymorphism in relation with hyperbilirubinemia in Indonesia, this study aims to explore incidence of SLCO1B1*1B polymorphism in Indonesia based on 3 hospitals from different provinces and population, and their association with hyperbilirubinemia severity.

METHODS

Our study included 88 neonates with mild and moderate-severe hyperbilirubinemia from 3 NICU in hospitals representing homogenous and heterogenous populations: Biak General Hospital Papua, Cipto Mangunkusumo Hospital (Jakarta), and M Yunus Hospital (Bengkulu). We collected samples between November 2016 and September 2017. DNA was obtained from existing samples of the patients from previous studies and were subjected to Polymerase Chain Reaction - Restriction Fragment Length Polymorphism (PCR-RFLP). We analyzed the *1B variant located in exon 5 of SLCO1B1 with TaqI restriction endonuclease. Clinical, demographic, and laboratory data was also collected from medical records and parents' interviews.

RESULTS

The most dominant variant of SLCO1B1*1B in our population is the homozygous G/G (68.18%), followed by heterozygous A/G (26.14%), and wild type A/A (5.68%). The heterozygous A/G had an Odds Ratio (OR) of 0.73 (95% CI 0.10-5.2) and homozygous G/G with OR of 0.51 (95%CI 0.08-3.27), both were not significant. Genotypic distribution across the different centers were also similar and not significant. The significant risk factors for moderate-severe hyperbilirubinemia were the population the neonate originated from (p = < 0.001) and the delivery location (p = 0.001), while SLCO1B1*1B was not associated with the different severity of hyperbilirubinemia.

CONCLUSIONS

SLCO1B1*1B is not associated with higher bilirubin levels among neonates with hyperbilirubinemia in Indonesia. Further study is needed to find other potentially important genetic polymorphisms in the development of severe hyperbilirubinemia in Indonesia.

Phototherapy for neonatal hyperbilirubinemia and childhood eczema, rhinitis and wheeze

BACKGROUND

The pathogenesis of allergic diseases in childhood may be attributed to influences of early environmental stimuli on fetal and neonatal immune regulation. Neonatal hyperbilirubinemia is common in the Asian population and up to 20% of infants require phototherapy. We examined the hypothesis that phototherapy for neonatal hyperbilirubinemia modulates the infant's risk of developing eczema, rhinitis and wheeze in the Growing Up in Singapore Towards healthy Outcomes (GUSTO) birth cohort.

METHOD

Interviewers collected information on demographics, lifestyle, birth data and allergic outcomes. Atopic sensitization was assessed through skin prick testing (SPT) to aeroallergens and food allergens.

RESULTS

A total of 135 (12.8%) children underwent phototherapy for neonatal hyperbilirubinemia. Infants who underwent phototherapy were of a significantly lower mean (SD) gestational age [37.5 (2.5) weeks] compared to those who did not [38.5 (1.2) weeks p < 0.01]. A higher proportion of infants born by Caesarean section underwent phototherapy compared to those who were born vaginally (17.5% vs 10.7%, p < 0.01). There were no differences in prevalence of allergen sensitization, eczema, rhinitis and early onset wheeze with use of nebulizer in the first 5 years of life between subjects that underwent phototherapy and those that did not. There were also no associations between mean bilirubin peak levels within the phototherapy group with development of eczema, rhinitis and early onset wheeze in the first 5 years of life.

CONCLUSION

We found no evidence for a link between phototherapy for neonatal hyperbilirubinemia and childhood allergic outcomes in this prospective mother-offspring cohort.

TRIAL REGISTRATION

NCT01174875 Registered 1 July 2010, retrospectively registered.

Systematic review of the clinical manifestations of glucose-6-phosphate dehydrogenase deficiency in the Greater Mekong Subregion: implications for malaria elimination and beyond

INTRODUCTION

To achieve malaria elimination in the Greater Mekong Subregion (GMS) by 2030, proper case management is necessary. 8-aminoquinolines, such as primaquine, are the only available medicines effective in preventing relapse of the hypnozoite stage of Plasmodium vivax, as well as the onward transmission of Plasmodium falciparum. However, primaquine can cause haemolysis in individuals who have glucose-6-phosphate dehydrogenase deficiency (G6PDd). We conducted a systematic review on the reported clinical manifestations of G6PDd to provide a comprehensive overview of the situation in the GMS.

METHODS

The protocol for this systematic review was registered on PROSPERO: International prospective register of systematic reviews (CRD42016043146). We searched the PubMed/MEDLINE, CINAHL, and Web of Science databases for published articles describing the clinical manifestations of G6PDd in the GMS. We included articles of all study designs from inception until 31 July 2016, reporting the clinical manifestations of G6PDd. We then performed a narrative synthesis of these articles.

RESULTS

We included 56 articles in this review, 45 of which were from Thailand. Haemolysis in G6PD-deficient individuals was caused not only by primaquine but also by other medicines and infections. Other clinical manifestations of G6PDd that were found were favism, neonatal jaundice and chronic non-spherocytic haemolytic anaemia. G6PDd also influenced the clinical presentations of genetic disorders and infections, such as thalassemia and typhoid fever.

CONCLUSION

As G6PDd also affects the clinical presentations of other infections, the benefits of G6PD testing and proper record keeping transcend those of malaria case management. Therefore, healthcare workers at the community level should be made familiar with complications resulting from G6PDd as these complications extend beyond the scope of malaria.

The Association between Prolonged Jaundice and UGT1A1 Gene Polymorphism (G71R) in Gilbert's Syndrome

INTRODUCTION

Jaundice is a common condition during the neonatal period. Prolonged jaundice occurs in a large number of breastfed infants. Considering the impact of genetic factors on the incidence of jaundice present study was conducted.

AIM

The aim of this study was to determine the association between prolonged jaundice and G71R polymorphism in Gilbert's syndrome.

MATERIALS AND METHODS

This case-control study was conducted at Taleghani Children's Hospital of Gorgan, Iran. The study group consisted of 87 icteric patients (aged more than 2 weeks) with an indirect bilirubin level higher than 10mg/dL. The control group consisted of 81 newborns without jaundice. The two groups were matched in terms of age and gender. DNA extraction was performed by "phenol-chloroform" method. Polymerase Chain Reaction with Confronting Two-Pair Primers (PCR-CTPP) was applied to amplify G71R polymorphism.

RESULTS

Overall, 84% and 64% of subjects in the study and control groups were male, respectively. The distribution of Gilbert genotype was not significantly different between the two groups (p=0.772). There was a correlation between prolonged jaundice in males and UGT1A1 G71R polymorphism (p =0.03). In the study group, 5(5.7%) subjects were homozygous (for A/A), 73 (83.9%) were heterozygous (for A/G), and 9(10.3%) were normal (for G/G). In the control group, 3(3.7%) participants were homozygous (A/A), 68(84%) were heterozygous (A/G) and 10 (12.3%) were normal (G/G).

CONCLUSION

There was no association between prolonged jaundice and G71R polymorphism, even though a relationship was revealed between male gender and the mentioned polymorphism.

Association of Neonatal Hyperbilirubinemia with UGT1A1 Gene Polymorphisms: A Meta-Analysis

Background

The results of studies on association between the polymorphisms in the coding region and the promoter of uridine diphosphateglucuronosyl transferase 1A1 (UGT1A1) and neonatal hyperbilirubinemia are controversial. This study aimed to determine whether the UGT1A1 gene polymorphisms of Gly71Arg and TATA promoter were significant risk factors associated with neonatal hyperbilirubinemia.

Material/Methods

The PubMed, Cochrane Library, and Embase databases were searched for papers that describe the association between UGT1A1 polymorphisms and neonatal hyperbilirubinemia. Summary odds ratios and 95% confidence intervals (CI) were estimated based on a fixed-effects model or random-effects model, depending on the absence or presence of significant heterogeneity.

Results

A total of 32 eligible studies and 6520 participants were identified. Among them, 24 studies focused on the association of neonatal hyperbilirubinemia with UGT1A1 Gly71Arg polymorphisms, and a significant difference was found for the comparison of AA vs. AG+GG (OR=3.47, 95% CI=2.29–5.28, P<0.0001). We included 19 studies on the association of neonatal hyperbilirubinemia with UGT1A1 TATA promoter polymorphism, which also found a statistically significant difference between 7/7 and 6/7 + 6/6 (OR=2.24, 95% CI=1.29–3.92, P=0.004).

Conclusions

This meta-analysis demonstrated that UGT1A1 polymorphisms (Gly71Arg and TATA promoter) significantly increase the risk of neonatal hyperbilirubinemia.

Neonatal bilirubin levels and childhood asthma in the US Collaborative Perinatal Project, 1959-1965

Evidence shows that asthma originates in early life. Studies have found that phototherapy and/or neonatal jaundice may be associated with asthma. We investigated the association between neonatal bilirubin levels and childhood asthma without phototherapy intervention in the Collaborative Perinatal Project, a multicenter prospective cohort study conducted in the United States from 1959 to 1965. A total of 54,795 livebirths were included, and 40,063 children were followed up until 7 years of age or older. Total serum bilirubin (TSB) levels were examined at 48 hours postpartum in newborns with birthweights of 2,250 g or more. Information on asthma and other diseases through age 7 years was summarized and confirmed by a group of pediatricians and child neurologists. Among 28,807 term infants, the overall prevalence of asthma was 5.26%. Risks of asthma increased with both maximum TSB levels and TSB levels at 48 hours postpartum (P for trend < 0.01). Neonatal maximum TSB levels greater than 15 mg/dL were associated with a 61% increase in the risk of childhood asthma (odds ratio = 1.61, 95% confidence interval: 1.04, 2.08) after adjustment for confounders. In this prospective cohort study of infants born at a time when phototherapy was unavailable, neonatal hyperbilirubinemia was associated with an increased risk of childhood asthma.

The impact of SLCO1B1 genetic polymorphisms on neonatal hyperbilirubinemia: a systematic review with meta-analysis

OBJECTIVE

To determine whether three variants (388 G>A, 521 T>C, and 463 C>A) of the solute carrier organic anion transporter family member 1B1 (SLCO1B1) are associated with neonatal hyperbilirubinemia.

DATA SOURCE

The China National Knowledge Infrastructure and MEDLINE databases were searched. The systematic review with meta-analysis included genetic studies which assessed the association between neonatal hyperbilirubinemia and 388 G>A, 521 T>C, and 463 C>A variants of SLCO1B1 between January of 1980 and December of 2012. Data selection and extraction were performed independently by two reviewers.

SUMMARY OF THE FINDINGS

Ten articles were included in the study. The results revealed that SLCO1B1 388 G>A is associated with an increased risk of neonatal hyperbilirubinemia (OR, 1.39; 95% CI, 1.07-1.82) in Chinese neonates, but not in white, Thai, Latin American, or Malaysian neonates. The SLCO1B1 521 T>C mutation showed a low risk of neonatal hyperbilirubinemia in Chinese neonates, while no significant associations were found in Brazilian, white, Asian, Thai, and Malaysian neonates. There were no significant differences in SLCO1B1 463 C>A between the hyperbilirubinemia and the control group.

CONCLUSION

This study demonstrated that the 388 G>A mutation of the SLCO1B1 gene is a risk factor for developing neonatal hyperbilirubinemia in Chinese neonates, but not in white, Thai, Brazilian, or Malaysian populations; the SLCO1B1 521 T>C mutation provides protection for neonatal hyperbilirubinemia in Chinese neonates, but not in white, Thai, Brazilian, or Malaysian populations.

UGT1A1, SLCO1B1, and SLCO1B3 polymorphisms vs. neonatal hyperbilirubinemia: is there an association?

BACKGROUND

Jaundice is a physiological phenomenon; however, severe hyperbilirubinemia occurs in only 5 to 6% of the healthy newborn population. It has been suggested that genetic variation could enhance the risk of hyperbilirubinemia when coexpressed with other icterogenic conditions.

METHODS

The study included newborns with a gestational age of greater than 35 wk and weights greater than 2,000 g with indications for phototherapy. The polymorphisms from UGT1A1 (rs8175347), SLCO1B1 (rs4149056 and rs2306283), and SLCO1B3 (rs17680137 and rs2117032) were analyzed by capillary electrophoresis and hydrolysis probes.

RESULTS

A total of 167 hyperbilirubinemic infants and 247 control subjects were enrolled. The gender, ABO incompatibility, birth weight, and gestational age differed between the groups, but the allelic and genotypic frequency of the polymorphisms from SLCO1B genes did not. In logistic regression, the ABO incompatibility, gestational age, and polymorphic T allele of rs2117032 remained in the model. The presence of this polymorphism seemed to provide protection from hyperbilirubinemia. The individuals who were homozygous for the G allele of rs2306283 and who were glucose 6-phosphate-dehydrogenase deficient were more frequent among the cases.

CONCLUSION

Although genetic variation accounts for a good part of this condition, the association between different polymorphisms and environmental factors has yet to be explained.

Association of neonatal hyperbilirubinemia with uridine diphosphate-glucuronosyltransferase 1A1 gene polymorphisms: meta-analysis

BACKGROUND

Recent reports have suggested that genetic factors, including mutations in the coding region or promoter of uridine diphosphate-glucuronosyltransferase 1A1 (UGT1A1) may increase the risk of development of neonatal hyperbilirubinemia, but the relationship has not been evaluated on systematic review or meta-analysis.

METHODS

A meta-analysis of observational studies reporting effect estimates and 95% confidence intervals (95%CI) was conducted on the association between UGT1A1 polymorphisms and neonatal hyperbilirubinemia.

RESULTS

A total of 27 eligible studies were identified. In total, 17 studies focused on the association of neonatal hyperbilirubinemia with UGT1A1 Gly71Arg polymorphisms, which indicated that these polymorphisms were associated with an increased risk of neonatal hyperbilirubinemia (A/A+G/A vs G/G: odds ratio [OR], 2.70; P= 0.00; 95%CI: 2.22-3.29; I(2) = 0.0%; P(heterogeneity) = 0.55). Subgroup analyses by ethnicity validated this correlation in Asian, but not in Caucasian, populations (OR, 1.74; P= 0.10; 95%CI: 0.90-3.35; I(2) = 0.00%; P(heterogeneity) = 0.67). Furthermore, 18 studies focused on the association of neonatal hyperbilirubinemia with UGT1A1 TATA promoter polymorphisms. These studies concluded that TATA promoter variants were not associated with an increased risk of neonatal hyperbilirubinemia (7/7 + 6/7 vs 6/6: OR, 1.13; P= 0.23; 95%CI: 0.93-1.37; I(2) = 80.0%; P(heterogeneity) = 0.00).

CONCLUSION

UGT1A1 Gly71Arg polymorphisms are a risk factor for developing neonatal hyperbilirubinemia in Asian, but not Caucasian, subjects. UGT1A1 TATA promoter polymorphisms were not associated with an increased risk of neonatal hyperbilirubinemia in Asian subjects, but results from the Caucasian population were conflicting and require further epidemiological investigation.

Neonatal hyperbilirubinemia and Gly71Arg mutation of UGT1A1 gene: a Chinese case-control study followed by systematic review of existing evidence

AIM

To determine whether the UDP-glucuronosyltransferase 1A1 gene (UGT1A1) Gly71Arg (211G>A) mutation is associated with neonatal hyperbilirubinemia.

METHODS

The study consisted of two parts. The case-control study included 112 hyperbilirubinemic infants and 105 control subjects from the Fifth People's Hospital of Shenzhen. Polymerase chain reaction, restriction fragment length polymorphisms and agarose gel electrophoresis techniques were used to detect the UGT1A1 211G>A mutation. Meta-analyses was performed to assess the association between neonatal hyperbilirubinemia and UGT1A1 211G>A.

RESULTS

Our case-control study revealed that the likelihood of developing neonatal hyperbilirubinemia was 2.65 times higher in the infants with the A allele in the UGT1A1 211G>A than in the infants with the G allele (95% CI, 1.60-4.39). Meta-analyses (including data from our study) revealed that UGT1A1 211G>A is associated with an increased risk of neonatal hyperbilirubinemia [odds ratio (OR), 2.37; 95% CI, 2.05-2.74]. In the subgroup analyses based on ethnicity, significantly elevated risks were found in Asian populations (OR, 2.45; 95% CI, 2.10-2.84), but no significant associations were present in Caucasian populations (OR, 1.54; 95% CI, 0.87-2.75).

CONCLUSION

  The UGT1A1 211G>A mutation is associated with neonatal hyperbilirubinemia in Asians, but not in Caucasians.

Exploring the genetic architecture of neonatal hyperbilirubinemia

The potential for genetic variation to modulate neonatal hyperbilirubinemia risk is increasingly being recognized. In particular, polymorphisms across three genes involved in bilirubin production and metabolism [glucose-6-phosphate dehydrogenase (G6PD), uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1), and solute carrier organic anion transporter polypeptide 1B1 (SLCO1B1)] may interact with each other and/or environmental contributors to produce significant hyperbilirubinemia. Variant gene co-expression including compound and synergistic heterozygosity enhances hyperbilirubinemia risk, contributing to the etiologic heterogeneity and complex nature of neonatal jaundice.