Low glucose-6-phosphate dehydrogenase enzyme activity level at the time of hemolysis in a male neonate with the African type of deficiency

Controversies in our understanding of extreme hyperbilirubinemia in glucose-6-phosphate dehydrogenase-deficient neonates

Despite declarations that kernicterus should be a "never-event", the condition continues to occur, glucose-6-phosphate dehydrogenase (G6PD)-deficiency being a leading cause. In this paper, we address some controversies regarding the pathophysiology and the potential for extreme hyperbilirubinemia associated with G6PD-deficiency. We present evidence to demonstrate that G6PD-deficiency-associated neonatal hyperbilirubinemia is no longer limited to countries and geographic regions to which the condition was indigenous, but is also encountered in North America and other Western countries with a low inherent G6PD-deficiency frequency. Pathophysiologically, while a diminished bilirubin conjugative component is undoubtedly present, we present evidence that there is a component of increased hemolysis as well, contributing to the extreme, exponential hyperbilirubinemia associated with G6PD-deficiency. Extreme hyperbilirubinemia in G6PD heterozygotes, while less frequent than in male hemizygotes or female deficient homozygotes, has been reported, suggesting previous underestimation of the risks of heterozygosity. Universal neonatal screening for G6PD-deficiency, while not expected to prevent acute, episodic hyperbilirubinemia, should increase awareness, thereby facilitating earlier referral for treatment, prior to the onset of bilirubin encephalopathy. Finally, we speculate as to what the future looks like for babies with G6PD-deficiency, potential therapeutic stratagems, and the effect of G6PD-deficiency on medical conditions beyond the realm of neonatal hyperbilirubinemia. IMPACT STATEMENTS: G6PD-deficiency is encountered in North America and Western countries previously thought to have a low frequency of the condition. Extreme, sudden neonatal hyperbilirubinemia is due, in the main, to increased hemolysis, an independent risk factor for neurotoxicity. Extreme hyperbilirubinemia may follow apparently resolved neonatal hyperbilirubinemia which had been treated by phototherapy. Female G6PD heterozygotes, previously thought to be unaffected clinically by G6PD-deficiency, while at low risk, may, nevertheless, develop extreme hyperbilirubinemia. Universal neonatal G6PD screening should be aimed towards increasing caretaker awareness and facilitating referral for treatment prior to the onset of bilirubin encephalopathy.

Glucose-6-phosphate dehydrogenase deficiency among neonates with jaundice in Africa; systematic review and meta-analysis

Background

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a genetic disorder caused by a structural abnormality in the enzyme. G6PD deficiency is most prevalent among African, Asian, and Mediterranean people. This study aimed to investigate how prevalent G6PD deficiency is in African neonates with jaundice.

Methods

The public sources, such as PubMed, Science Direct, Google Scholar, and Africa Journal Online were searched for articles that reported the prevalence of G6PD deficiency published before March 21st, 2022. The Joanna Briggs Institute's (JBI) critical assessment checklist was used to evaluate the quality of individual studies. STATA-17 was used to do the statistical analysis. The pooled prevalence of G6PD deficiency in neonates with jaundice in Africa was calculated using a forest plot and a random effects model. I2 statistics and Galbraith plots were used to assess heterogeneity. Publication bias was assessed using a funnel plot and Egger's statistical test.

Results

Ten studies involving 1555 neonates with jaundice were involved in the study. G6PD deficiency was prevalent in 24.60% of African neonates with jaundice (95% CI:12.47-36.74) with considerable heterogeneity (I2 = 100%). Nigerian neonates with jaundice had the highest G6PD deficiency (49.67%), whereas South Africans had the lowest (3.14%).

Conclusion

G6PD deficiency has been implicated in a significant portion of African neonates with jaundice, notwithstanding the need for greater research on predisposing variables from other countries. Therefore, it should be thought of performing screening and diagnostic laboratory tests for G6PD deficiency.

A novel point-of-care device for measuring glucose-6-phosphate dehydrogenase enzyme deficiency

Extreme hyperbilirubinemia can cause bilirubin neurotoxicity. Infants with glucose-6-phosphate dehydrogenase (G6PD) deficiency can develop hemolysis and thus are at high risk. We evaluated a device that quantitatively measures G6PD activity kinetically using digital microfluidics (DMF). Intra- and inter-instrument and -day imprecision (CVs) were first assessed. G6PD activity in 86 samples was then measured and compared between DMF and 2 reference methods. Overall DMF reproducibility was 3.8% over 5 days by 2 operators on 2 instruments. Mean intra- and inter-instrument variabilities were 3.6% and 3.9%, respectively (n = 28), with a user variability of 4.3%. Mean G6PD activity was 6.40±4.62 and 6.37±4.62 U/g hemoglobin for DMF and Reference Methods 1 (n = 46) and 12.15±3.86 and 11.48±1.55 for DMF and 2 (n = 40), respectively, and strongly correlated (r = 0.95 and 0.95) with mean biases of +0.04±2.90 and +0.67±1.55 for methods 1 and 2, respectively. The novel device could be used for early newborn G6PD screening.

Glucose-6-phosphate dehydrogenase deficiency in triplets of African-American descent

Despite the prevalence of glucose-6-phosphate dehydrogenase (G6PD) deficiency in African Americans, the disorder maybe often overlooked as a diagnosis in the absence of overt signs of hemolysis in neonates with hyperbilirubinemia. We present a case report of anemia and prolonged hyperbilirubinemia due to G6PD deficiency in the absence of hemolysis in dichorionic, triamniotic, preterm triplets of African-American descent.

Pharmacogenomics of human UDP-glucuronosyltransferase enzymes

UDP-glucuronosyltransferase (UGT) enzymes comprise a superfamily of key proteins that catalyze the glucuronidation reaction on a wide range of structurally diverse endogenous and exogenous chemicals. Glucuronidation is one of the major phase II drug-metabolizing reactions that contributes to drug biotransformation. This biochemical process is also involved in the protection against environmental toxicants, carcinogens, dietary toxins and participates in the homeostasis of numerous endogenous molecules, including bilirubin, steroid hormones and biliary acids. Over the years, significant progress was made in the field of glucuronidation, especially with regard to the identification of human UGTs, study of their tissue distribution and substrate specificities. More recently, the degree of allelic diversity has also been revealed for several human UGT genes. Some polymorphic UGTs have demonstrated a significant pharmacological impact in addition to being relevant to drug-induced adverse reactions and cancer susceptibility. This review focuses on human UGTs, the description of the nature of polymorphic variations and their functional impact. The pharmacogenomic implication of polymorphic UGTs is presented, more specifically the role of UGT polymorphisms in modifying cancer risk and their impact on individual risk to drug-induced toxicities.

Severe jaundice in a patient with a previously undescribed glucose-6-phosphate dehydrogenase (G6PD) mutation and Gilbert syndrome

A patient with chronic hemolytic anemia and G6PD deficiency was noted to be severely jaundiced and to have a high serum ferritin level. Analysis of his DNA revealed only heterozygosity for the c.187 C-->G (H63D) mutation of HFE, but showed that he was homozygous for the UDP glucuronosyltransferase promoter mutation of Gilbert's disease and that he had a previously undescribed mutation of G6PD, c.832 T-->C (Ser278Pro). The new variant was named G6PD La Jolla.