Diagnosis and clinical management of enzymopathies.

At least 16 genetically determined conditions qualify as red blood cell enzymopathies. They range in frequency from ultrarare to rare, with the exception of glucose-6-phosphate dehydrogenase deficiency, which is very common. Nearly all these enzymopathies manifest as chronic hemolytic anemias, with an onset often in the neonatal period. The diagnosis can be quite easy, such as when a child presents with dark urine after eating fava beans, or it can be quite difficult, such as when an adult presents with mild anemia and gallstones. In general, 4 steps are recommended: (1) recognizing chronic hemolytic anemia; (2) excluding acquired causes; (3) excluding hemoglobinopathies and membranopathies; (4) pinpointing which red blood cell enzyme is deficient. Step 4 requires 1 or many enzyme assays; alternatively, DNA testing against an appropriate gene panel can combine steps 3 and 4. Most patients with a red blood cell enzymopathy can be managed by good supportive care, including blood transfusion, iron chelation when necessary, and splenectomy in selected cases; however, some patients have serious extraerythrocytic manifestations that are difficult to manage. In the absence of these, red blood cell enzymopathies are in principle amenable to hematopoietic stem cell transplantation and gene therapy/gene editing.

Genotypic glucose-6-phosphate dehydrogenase (G6PD) deficiency protects against Plasmodium falciparum infection in individuals living in Ghana.

INTRODUCTION: The global effort to eradicate malaria requires a drastic measure to terminate relapse from hypnozoites as well as transmission via gametocytes in malaria-endemic areas. Primaquine has been recommended for the treatment of P. falciparum gametocytes and P. vivax hypnozoites, however, its implementation is challenged by the high prevalence of G6PD deficient (G6PDd) genotypes in malaria endemic countries. The objective of this study was to profile G6PDd genotypic variants and correlate them with malaria prevalence in Ghana. METHODS: A cross-sectional survey of G6PDd genotypic variants was conducted amongst suspected malaria patients attending health care facilities across the entire country. Malaria was diagnosed using microscopy whilst G6PD deficiency was determined using restriction fragment length polymorphisms at position 376 and 202 of the G6PD gene. The results were analysed using GraphPad prism. RESULTS: A total of 6108 subjects were enrolled in the study with females representing 65.59% of the population. The overall prevalence of malaria was 36.31%, with malaria prevalence among G6PDd genotypic variants were 0.07% for A-A- homozygous deficient females, 1.31% and 3.03% for AA- and BA- heterozygous deficient females respectively and 2.03% for A- hemizygous deficient males. The odd ratio (OR) for detecting P. falciparum malaria infection in the A-A- genotypic variant was 0.0784 (95% CI: 0.0265-0.2319, p<0.0001). Also, P. malariae and P. ovale parasites frequently were observed in G6PD B variants relative to G6PD A- variants. CONCLUSION: G6PDd genotypic variants, A-A-, AA- and A- protect against P. falciparum, P. ovale and P. malariae infection in Ghana.

Association of alpha-thalassemia and Glucose-6-Phosphate Dehydrogenase deficiency with transcranial Doppler ultrasonography in Nigerian children with sickle cell anemia.

BACKGROUND: Stroke is a devastating complication of sickle cell anemia (SCA) and can be predicted through abnormally high cerebral blood flow velocity using transcranial Doppler Ultrasonography (TCD). The evidence on the role of alpha-thalassemia and glucose-6-phosphate dehydrogenase (G6PD) deficiency in the development of stroke in children with SCA is conflicting. Thus, this study investigated the association of alpha-thalassemia and G6PD(A- ) variant with abnormal TCD velocities among Nigerian children with SCA. METHODS: One hundred and forty-one children with SCA were recruited: 72 children presented with normal TCD (defined as the time-averaged mean of the maximum velocity: < 170 cm/s) and 69 children with abnormal TCD (TAMMV ≥ 200 cm/s). Alpha-thalassemia (the α-3.7 globin gene deletion) was determined by multiplex gap-PCR, while G6PD polymorphisms (202G > A and 376A > G) were genotyped using restriction fragment length polymorphism-polymerase chain reaction. RESULTS: The frequency of α-thalassemia trait in the children with normal TCD was higher than those with abnormal TCD: 38/72 (52.8%) [α-/ α α: 41.7%, α -/ α -: 11.1%] versus 21/69 (30.4%) [α-/ α α: 27.5%, α -/ α -: 2.9%], and the odds of abnormal TCD were reduced in the presence of the α-thalassemia trait [Odds Ratio: 0.39, 95% confidence interval: 0.20-0.78, p = 0.007]. However, the frequencies of G6PDA- variant in children with abnormal and normal TCD were similar (11.6% vs. 15.3%, p = 0.522). CONCLUSION: Our study reveals the protective role of α-thalassemia against the risk of abnormal TCD in Nigerian children with SCA.

Deficiency of Mitochondrial Glycerol 3-Phosphate Dehydrogenase Exacerbates Podocyte Injury and the Progression of Diabetic Kidney Disease.

Mitochondrial function is essential for bioenergetics, metabolism, and signaling and is compromised in diseases such as proteinuric kidney diseases, contributing to the global burden of kidney failure, cardiovascular morbidity, and death. The key cell type that prevents proteinuria is the terminally differentiated glomerular podocyte. In this study, we characterized the importance of mitochondrial glycerol 3-phosphate dehydrogenase (mGPDH), located on the inner mitochondrial membrane, in regulating podocyte function and glomerular disease. Specifically, podocyte-dominated mGPDH expression was downregulated in the glomeruli of patients and mice with diabetic kidney disease and adriamycin nephropathy. Podocyte-specific depletion of mGPDH in mice exacerbated diabetes- or adriamycin-induced proteinuria, podocyte injury, and glomerular pathology. RNA sequencing revealed that mGPDH regulated the receptor for the advanced glycation end product (RAGE) signaling pathway, and inhibition of RAGE or its ligand, S100A10, protected against the impaired mitochondrial bioenergetics and increased reactive oxygen species generation caused by mGPDH knockdown in cultured podocytes. Moreover, RAGE deletion in podocytes attenuated nephropathy progression in mGPDH-deficient diabetic mice. Rescue of podocyte mGPDH expression in mice with established glomerular injury significantly improved their renal function. In summary, our study proposes that activation of mGPDH induces mitochondrial biogenesis and reinforces mitochondrial function, which may provide a potential therapeutic target for preventing podocyte injury and proteinuria in diabetic kidney disease.

COVID-19 may enhance risk of thrombosis and hemolysis in the G6PD deficient patients.

COVID-19 has become a major public health problem since December, 2019 and no highly effective drug has been found until now. Numbers of infected people and deaths by COVID-19 are increasing every day worldwide, therefore self-isolation and protection are highly recommended to prevent the spread of the virus and especially to protect major risk groups such as the elderly population and people with comorbidities including diabetes, hypertension, cancer, cardiovascular diseases and metabolic syndrome. On the other hand, young people without any secondary disease have died by COVID-19 as well. In this study we compared two male patients infected by COVID-19 at the same age and one of them was diagnosed with G6PD deficiency. Both COVID-19 and G6PD deficiency enhance the risk of hemolysis and thrombosis. Serum biochemistry, hemogram and immunological parameters showed that risk of hemolysis and thrombosis may increase in the G6PD deficient patient infected by COVID-19.

Long-range structural defects by pathogenic mutations in most severe glucose-6-phosphate dehydrogenase deficiency.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common blood disorder, presenting multiple symptoms, including hemolytic anemia. It affects 400 million people worldwide, with more than 160 single mutations reported in G6PD. The most severe mutations (about 70) are classified as class I, leading to more than 90% loss of activity of the wild-type G6PD. The crystal structure of G6PD reveals these mutations are located away from the active site, concentrating around the noncatalytic NADP+-binding site and the dimer interface. However, the molecular mechanisms of class I mutant dysfunction have remained elusive, hindering the development of efficient therapies. To resolve this, we performed integral structural characterization of five G6PD mutants, including four class I mutants, associated with the noncatalytic NADP+ and dimerization, using crystallography, small-angle X-ray scattering (SAXS), cryogenic electron microscopy (cryo-EM), and biophysical analyses. Comparisons with the structure and properties of the wild-type enzyme, together with molecular dynamics simulations, bring forward a universal mechanism for this severe G6PD deficiency due to the class I mutations. We highlight the role of the noncatalytic NADP+-binding site that is crucial for stabilization and ordering two ß-strands in the dimer interface, which together communicate these distant structural aberrations to the active site through a network of additional interactions. This understanding elucidates potential paths for drug development targeting G6PD deficiency.

Cyanosis Due to Methemoglobinemia as the Presenting Sign of Glucose-6-Phosphate Dehydrogenase Deficiency in a Child: Diagnostic and Clinical Implications.

A previously healthy 3-year-old boy presented with pallor, jaundice, cyanosis, and a 24-hour history of vomiting and anorexia following fava bean ingestion. Clinical examination and laboratory findings were consistent with severe nonimmune hemolytic anemia with methemoglobinemia. Given the patient's history, a previously unrecognized glucose-6-phosphate dehydrogenase deficiency was suspected and diagnosed. The aim of this article is to delineate the possible coexistence of methemoglobinemia and glucose-6-phosphate dehydrogenase deficiency in children presented with acute hemolysis and discuss its management while reviewing the existing literature.

Brief Report: Hydroxychloroquine does not induce hemolytic anemia or organ damage in a "humanized" G6PD A- mouse model.

BACKGROUND: Hydroxychloroquine (HCQ) is widely used in the treatment of malaria, rheumatologic disease such as lupus, and most recently, COVID-19. These uses raise concerns about its safe use in the setting of glucose-6-phosphate dehydrogenase (G6PD) deficiency, especially as 11% of African American men carry the G6PD A- variant. However, limited data exist regarding the safety of HCQ in this population. STUDY DESIGN AND METHODS: Recently, we created a novel "humanized" mouse model containing the G6PD deficiency A- variant (Val68Met) using CRISPR technology. We tested the effects of high-dose HCQ administration over 5 days on hemolysis in our novel G6PD A- mice. In addition to standard hematologic parameters including plasma hemoglobin, erythrocyte methemoglobin, and reticulocytes, hepatic and renal function were assessed after HCQ. RESULTS: Residual erythrocyte G6PD activity in G6PD A- mice was ~6% compared to wild-type (WT) littermates. Importantly, we found no evidence of clinically significant intravascular hemolysis, methemoglobinemia, or organ damage in response to high-dose HCQ. CONCLUSIONS: Though the effects of high doses over prolonged periods was not assessed, this study provides early, novel safety data of the use of HCQ in the setting of G6PD deficiency secondary to G6PD A-. In addition to novel safety data for HCQ, to our knowledge, we are the first to present the creation of a "humanized" murine model of G6PD deficiency.

A novel G6PD deleterious variant identified in three families with severe glucose-6-phosphate dehydrogenase deficiency.

BACKGROUND: Glucose-6-phosphate dehydrogenase deficiency (D-G6PD) is an X-linked recessive disorder resulted from deleterious variants in the housekeeping gene Glucose-6-phosphate 1-dehydrogenase (G6PD), causing impaired response to oxidizing agents. Screening for new variations of the gene helps with early diagnosis of D-G6PD resulting in a reduction of disease related complications and ultimately increased life expectancy of the patients. METHODS: One thousand five hundred sixty-five infants with pathological jaundice were screened for G6PD variants by Sanger sequencing all of the 13 exons, and the junctions of exons and introns of the G6PD gene. RESULTS: We detected G6PD variants in 439 (28.1%) of the 1565 infants with pathological jaundice. In total, 9 types of G6PD variants were identified in our cohort; and a novel G6PD missense variant c.1118 T > C, p.Phe373Ser in exon 9 of the G6PD gene was detected in three families. Infants with this novel variant showed decreased activity of G6PD, severe anemia, and pathological jaundice, consistent with Class I G6PD deleterious variants. Analysis of the resulting protein's structure revealed this novel variant affects G6PD protein stability, which could be responsible for the pathogenesis of D-G6PD in these patients. CONCLUSIONS: High rates of G6PD variants were detected in infants with pathological jaundice, and a novel Class I G6PD deleterious variants was identified in our cohort. Our data reveal that variant analysis is helpful for the diagnosis of D-G6PD in patients, and also for the expansion of the spectrum of known G6PD variants used for carrier detection and prenatal diagnosis.

The New CIC Mutation Associates with Mental Retardation and Severity of Seizure in Turkish Child with a Rare Class I Glucose-6-Phosphate Dehydrogenase Deficiency.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked recessive disease that causes acute or chronic hemolytic anemia and potentially leads to severe jaundice in response to oxidative agents. Capicua transcriptional repressor (CIC) is an important gene associated with mental retardation, autosomal dominant 45. Affiliated tissues including skin, brain, bone, and related phenotypes are intellectual disability and seizures. Clinical, biochemical, and whole exome analysis are carried out in a Turkish family. Mutation analysis of G6PD and CIC genes by Sanger sequencing in the whole family was carried out to reveal the effect of these mutations on the patient's clinical outcome. Here, we present the case of epilepsy in an 8-year-old child with a hemizygous variation in G6PD gene and heterozygous mutation in CIC gene, resulting in focal epileptiform activity and hypsarrhythmia in electroencephalography (EEG), seizures, psychomotor retardation, speech impairment, intellectual disability, developmental regression, and learning difficulties. Whole exome sequencing confirmed the diagnosis of X-linked increased susceptibility for hemolytic anemia due to G6PD deficiency and mental retardation type 45 due to CIC variant, which explained the development of epileptic seizures. Considering CIC variant and relevant relation with the severity and course of the disease, G6PD mutations sustained through the family are defined as hereditary. Our findings could represent the importance of variants found in G6PD as well as CIC genes linked to the severity of epilepsy, which was presumed based on the significant changes in protein configuration.

Donor glucose-6-phosphate dehydrogenase deficiency decreases blood quality for transfusion.

BACKGROUNDGlucose-6-phosphate dehydrogenase (G6PD) deficiency decreases the ability of red blood cells (RBCs) to withstand oxidative stress. Refrigerated storage of RBCs induces oxidative stress. We hypothesized that G6PD-deficient donor RBCs would have inferior storage quality for transfusion as compared with G6PD-normal RBCs.METHODSMale volunteers were screened for G6PD deficiency; 27 control and 10 G6PD-deficient volunteers each donated 1 RBC unit. After 42 days of refrigerated storage, autologous 51-chromium 24-hour posttransfusion RBC recovery (PTR) studies were performed. Metabolomics analyses of these RBC units were also performed.RESULTSThe mean 24-hour PTR for G6PD-deficient subjects was 78.5% ± 8.4% (mean ± SD), which was significantly lower than that for G6PD-normal RBCs (85.3% ± 3.2%; P = 0.0009). None of the G6PD-normal volunteers (0/27) and 3 G6PD-deficient volunteers (3/10) had PTR results below 75%, a key FDA acceptability criterion for stored donor RBCs. As expected, fresh G6PD-deficient RBCs demonstrated defects in the oxidative phase of the pentose phosphate pathway. During refrigerated storage, G6PD-deficient RBCs demonstrated increased glycolysis, impaired glutathione homeostasis, and increased purine oxidation, as compared with G6PD-normal RBCs. In addition, there were significant correlations between PTR and specific metabolites in these pathways.CONCLUSIONBased on current FDA criteria, RBCs from G6PD-deficient donors would not meet the requirements for storage quality. Metabolomics assessment identified markers of PTR and G6PD deficiency (e.g., pyruvate/lactate ratios), along with potential compensatory pathways that could be leveraged to ameliorate the metabolic needs of G6PD-deficient RBCs.TRIAL REGISTRATIONClinicalTrials.gov NCT04081272.FUNDINGThe Harold Amos Medical Faculty Development Program, Robert Wood Johnson Foundation grant 71590, the National Blood Foundation, NIH grant UL1 TR000040, the Webb-Waring Early Career Award 2017 by the Boettcher Foundation, and National Heart, Lung, and Blood Institute grants R01HL14644 and R01HL148151.

Prevalence of UGT1A1 (TA)n promoter polymorphism in Panamanians neonates with G6PD deficiency.

A relationship between the polymorphism in promoter region of the UGT1A1 gene and the development of jaundice has been demonstrated recently. This polymorphism leads to 30% of normal rate transcription initiation of UGT1A1 gene, thus decreasing the bilirubin glucuronidation. The combination of the G6PD deficiency and polymorphism in neonates and adults may causepronounced hyperbilirubinaemias. The aim of this study was to analyse the variations in the UGT1A1 gene promoter in Panamanians neonates with G6PD deficiency and its association with neonatal jaundice (NJ). We identified five different genotypes of TA repeats, in 17 neonates (42.5%) the normal variant TA6/TA6 and in the other 57.5% of the subjects: TA7/TA7 (12.5%), TA6/TA7 (40%), TA6/TA8 (2.5%) and TA6/TA5 (2.5%). Additionally 75% of the 16 newborns that showed NJ had an abnormal variant in the promotersequence, although, there was no significant difference (P = 0.068). The risk of jaundice in neonates with TA7 variant was thrice higher in subjects than with other alleles (P = 0.093, CI: 0.81-11.67). The TA7 allele frequency in this study (0.325) was consistent with the global frequency and similar to Caucasians. The results proved that there is no significant relationship between promoter polymorphism in UGT1A1 and NJ in G6PD deficient Panamanian newborns. Further studies with a greater number of subjects would determine the exact relationship between marked NJ and UGT1A promoter variations.

Genotyping of Malaysian G6PD-deficient neonates by reverse dot blot flow-through hybridisation.

G6PD deficiency is the commonest enzyme deficiency found in humans. Current diagnostic methods lack sensitivity to detect all cases of G6PD deficiency. We evaluated the reverse dot blot flow-through hybridisation assay designed to detect simultaneously multiple known G6PD mutations in a group of Malaysian neonates. Archival DNA samples from 141 G6PD-deficient neonates were subjected to reverse dot blot flow-through hybridisation assay using the GenoArray Diagnostic Kit (Hybribio Limited, Hong Kong) and DNA sequencing. The method involved PCR amplification of 5 G6PD exons using biotinylated primers, hybridisation of amplicons to a membrane containing oligoprobes designed for G6PD mutations known to occur in the Malaysian population and colour detection by enzyme immunoassay. The assay detected 13 of the 14 G6PD mutations and genotyped 133 (94.3%) out of 141 (102 males, 39 females) cases. Among the 39 female G6PD-deficient neonates, there were 7 homozygous and 6 compound heterozygous cases. The commonest alleles were G6PD Viangchan 871G > A (21%) and G6PD Mahidol 487G > A(20%) followed by G6PD Mediterranean 563C > T, (14%), G6PD Vanua Lava 383T > C (12%), G6PD Canton 1376G > T (10%), G6PD Orissa 131C > G (6.3%) G6PD Coimbra 592C > T (5.6%) plus 6 other mutations. DNA sequencing of remaining cases revealed 6 cases of intron 11 nt 93C > T not previously reported in Malaysia and two novel mutations, one case each of nt 1361G > T and nt 1030G > A. We found the reverse dot blot assay easy to perform, rapid, accurate and reproducible, potentially becoming an improved diagnostic test for G6PD deficiency.

A typical presentation of dengue fever in a G6PD deficient patient: A case report.

Dengue is a mosquito-borne viral disease that has rapidly spread in the recent years, particularly in South Asia. While haematologic complications, such as cytopenia and bleeding, may occur in severe dengue infection, reports of haemolytic anaemia in dengue fever are scant. We report a patient who developed haemolytic anaemia following dengue fever. A 45 years old gentleman presented with five-day history of fever and was recently diagnosed with dengue fever. He developed jaundice and started vomiting on the third day of his clinical course. His laboratory investigations revealed deranged liver profile, Coombs negative haemolytic anaemia and G6PD deficiency. He was treated conservatively with fluids and blood transfusions. His liver functions and haemolytic anaemia gradually resolved. This case highlights the importance of recognising dengue fever-induced haemolytic anaemia in a G6PD deficient patient by physicians and pathologists, enabling better diagnosis and improved management of this life-threatening condition.