Identification of G6PD Mediterranean mutation by amplification refractory mutation system

Rapid and reliable detection of G6PD mutations using recombinase polymerase amplification coupled with lateral flow strip

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzymopathy, affecting approximately 500 million people worldwide. It results from inherited mutations in the G6PD gene, causing increased susceptibility to drug-induced hemolytic anemia and severe neonatal jaundice. While phenotypic tests are commonly used, genetic testing is increasingly recognized for its value in the accurate diagnosis of G6PD deficiency, especially in heterozygous females and newborns. This study aimed to develop and evaluate a rapid, field-deployable genetic test for the detection of four common G6PD variants in Thailand: G6PD Gaohe (c.95A > G), G6PD Mahidol (c.487G > A), G6PD Viangchan (c.871G > A), and G6PD Canton (c.1376G > T). The assays utilize recombinase polymerase amplification with allele-specific primers incorporating locked nucleic acids to enhance specificity, followed by lateral flow strip detection for visual readout. The assays deliver results within 45 min at 37 ˚C. Singleplex detection demonstrated 100 % diagnostic sensitivity (Confidence interval (CI): 95.01-100.0 %) and specificity (CI: 95.49-100.0 %). Duplex assays (Gaohe + Canton and Mahidol + Viangchan) also demonstrated 100 % diagnostic sensitivity (CI: 94.87-100.0 %) and specificity (CI: 91.19-100.0 %). Limits of detection (LOD) for singleplex assays were 0.25, 1.00, 0.50, and 0.50 ng/µL, for Gaohe, Mahidol, Viangchan, and Canton, respectively. Duplex assays showed LODs of 0.10 ng/μL for Mahidol + Viangchan and 10.00  ng/μL for Gaohe + Canton. Band intensity differences ranged from 5.25 to 19.61 pixels between mutant, wild-type, and nontarget alleles, enabling clear allele discrimination. This innovative diagnostic tool offers a rapid, reliable, and accessible solution for point-of-care genetic testing, with the potential to improve clinical management and healthcare outcomes in regions with a high burden of G6PD deficiency.

Improved genetic screening with zygosity detection through multiplex high-resolution melting curve analysis and biochemical characterisation for G6PD deficiency

Accurate diagnosis of glucose-6-phosphate dehydrogenase (G6PD) deficiency is crucial for relapse malaria treatment using 8-aminoquinolines (primaquine and tafenoquine), which can trigger haemolytic anaemia in G6PD-deficient individuals. This is particularly important in regions where the prevalence of G6PD deficiency exceeds 3%-5%, including Southeast Asia and Thailand. While quantitative phenotypic tests can identify women with intermediate activity who may be at risk, they cannot unambiguously identify heterozygous females who require appropriate counselling. This study aimed to develop a genetic test for G6PD deficiency using high-resolution melting curve analysis, which enables zygosity identification of 15 G6PD alleles. In 557 samples collected from four locations in Thailand, the prevalence of G6PD deficiency based on indirect enzyme assay was 6.10%, with 8.08% exhibiting intermediate deficiency. The developed high-resolution melting assays demonstrated excellent performance, achieving 100% sensitivity and specificity in detecting G6PD alleles compared with Sanger sequencing. Genotypic variations were observed across four geographic locations, with the combination of c.1311C>T and c.1365-13T>C being the most common genotype. Compound mutations, notably G6PD Viangchan (c.871G>A, c.1311C>T and c.1365-13T>C), accounted for 15.26% of detected mutations. The high-resolution melting assays also identified the double mutation G6PD Chinese-4 + Canton and G6PD Radlowo, a variant found for the first time in Thailand. Biochemical and structural characterisation revealed that these variants significantly reduced catalytic activity by destabilising protein structure, particularly in the case of the Radlowo mutation. The refinement of these high-resolution melting assays presents a highly accurate and high-throughput platform that can improve patient care by enabling precise diagnosis, supporting genetic counselling and guiding public health efforts to manage G6PD deficiency-especially crucial in malaria-endemic regions where 8-aminoquinoline therapies pose a risk to deficient individuals.

Mutation-Selected Amplification droplet digital PCR: A new single nucleotide variant detection assay for TP53R249S mutant in tumor and plasma samples

The early detection of gene mutations in physiological and pathological processes is a powerful approach to guide decisions in precision medicine. However, detecting low-copy mutant DNA from clinical samples poses a challenge due to the enrichment of wild-type DNA backgrounds. In this study, we devised a novel strategy, named Mutation-Selected Amplification droplet digital PCR (MSA-ddPCR), to quantitatively analyze single nucleotide variants (SNVs) at low variant allele frequencies (VAFs). Using TP53R249S (a hotspot mutation associated with hepatocellular carcinoma) as a model, we optimized the concentration ratio of primers, the annealing temperature and nucleic acid amplification modifiers. Subsequently, we evaluated the linear range and precision of MSA-ddPCR by detecting TP53R249S and TP53wild-type (TP53WT) plasmid DNA, respectively. MSA-ddPCR demonstrated superior ability to discriminate between mutant DNA and wild-type DNA compared to traditional TaqMan-MGB PCR. We further applied MSA-ddPCR to analyze the TP53R249S mutation in 20 plasma samples and 15 formalin-fixed paraffin-embedded (FFPE) tissue samples, and assessed the agreement rates between MSA-ddPCR and amplicon high-throughput sequencing. The results showed that the limit of blanks of MSA-ddPCR are 0.449 copies μL-1 in the FAM channel and 0.452 copies μL-1 in the VIC channel. MSA-ddPCR could accurately quantify VAFs as low as 0.01 %, surpassing existing PCR and next-generation sequencing (NGS) methods. In the detection of clinical samples, a high correlation was found between MSA-ddPCR and amplicon high-throughput sequencing. Additionally, MSA-ddPCR outperformed sequencing methods in terms of detection time and simplicity of data analysis. MSA-ddPCR can be easily implemented into clinical practice and serve as a robust tool for detecting mutant genes due to its high sensitivity and accuracy.

Single-Drop Blood Detection of Common G6PD Mutations in Thailand Based on Allele-Specific Recombinase Polymerase Amplification with CRISPR-Cas12a

Glucose 6-phosphate dehydrogenase (G6PD) deficiency is the most common inherited enzymopathy. Identification of the G6PD deficiency through screening is crucial to preventing adverse effects associated with hemolytic anemia following antimalarial drug exposure. Therefore, a rapid and precise field-based G6PD deficiency diagnosis is required, particularly in rural regions where malaria is prevalent. The phenotypic diagnosis of the G6PD intermediate has also been a challenging issue due to the overlapping of G6PD activity levels between deficient and normal individuals, leading to a misinterpretation. The availability of an accurate point-of-care testing (POCT) for G6PD genotype diagnosis will therefore increase the opportunity for screening heterozygous cases in a low-resource setting. In this study, an allele-specific recombinase polymerase amplification (AS RPA) with clustered regularly interspaced short palindromic repeats-Cas12a (CRISPR-Cas12a) was developed as a POCT for accurate diagnosis of common G6PD mutations in Thailand. The AS primers for the wild type and mutant alleles of G6PD MahidolG487A and G6PD ViangchanG871A were designed and used in RPA reactions. Following application of CRISPR-Cas12a systems containing specific protospacer adjacent motif, the targeted RPA amplicons were visualized with the naked eye. Results demonstrated that the G6PD MahidolG487A and G6PD ViangchanG871A assays reached 93.62 and 98.15% sensitivity, respectively. The specificity was 88.71% in MahidolG487A and 99.02% in G6PD ViangchanG871A. The diagnosis accuracy of the G6PD MahidolG487A and G6PD ViangchanG871A assays was 91.67 and 98.72%, respectively. From DNA extraction to detection, the assay required approximately 52 min. In conclusion, this study demonstrated the high performance of an AS RPA with the CRISPR-Cas12a platform for G6PD MahidolG487A and G6PD ViangchanG871A detection assays and the potential use of G6PD genotyping as POCT.

Molecular characterization of G6PD mutations identifies new mutations and a high frequency of intronic variants in Thai females

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked enzymopathy caused by mutations in the G6PD gene. A medical concern associated with G6PD deficiency is acute hemolytic anemia induced by certain foods, drugs, and infections. Although phenotypic tests can correctly identify hemizygous males, as well as homozygous and compound heterozygous females, heterozygous females with a wide range of G6PD activity may be misclassified as normal. This study aimed to develop multiplex high-resolution melting (HRM) analyses to enable the accurate detection of G6PD mutations, especially among females with heterozygous deficiency. Multiplex HRM assays were developed to detect six G6PD variants, i.e., G6PD Gaohe (c.95A>G), G6PD Chinese-4 (c.392G>T), G6PD Mahidol (c.487G>A), G6PD Viangchan (c.871G>A), G6PD Chinese-5 (c.1024C>T), and G6PD Union (c.1360C>T) in two reactions. The assays were validated and then applied to genotype G6PD mutations in 248 Thai females. The sensitivity of the HRM assays developed was 100% [95% confidence interval (CI): 94.40%-100%] with a specificity of 100% (95% CI: 88.78%-100%) for detecting these six mutations. The prevalence of G6PD deficiency was estimated as 3.63% (9/248) for G6PD deficiency and 31.05% (77/248) for intermediate deficiency by phenotypic assay. The developed HRM assays identified three participants with normal enzyme activity as heterozygous for G6PD Viangchan. Interestingly, a deletion in intron 5 nucleotide position 637/638 (c.486-34delT) was also detected by the developed HRM assays. G6PD genotyping revealed a total of 12 G6PD genotypes, with a high prevalence of intronic variants. Our results suggested that HRM analysis-based genotyping is a simple and reliable approach for detecting G6PD mutations, and could be used to prevent the misdiagnosis of heterozygous females by phenotypic assay. This study also sheds light on the possibility of overlooking intronic variants, which could affect G6PD expression and contribute to enzyme deficiency.

p.Asn77Lys homozygous CLN6 mutation in two unrelated Japanese patients with Kufs disease, an adult onset neuronal ceroid lipofuscinosis

BACKGROUND

The neuronal ceroid lipofuscinosis (NCL) are a group of autosomal recessive neurodegenerative disorders that are characterized by the accumulation of ceroid lipofuscins. The NCLs are categorized into four classes based on the age of onset. Kufs disease is a rare adult-onset NCL caused by mutations in the CLN6 gene, which is rarely observed in the Japanese population.

CASE

We previously reported a case study on a patient with Kufs disease, whose parents had a consanguineous marriage. Later, we observed another unrelated patient with Kufs. Here we present the case and mutational gene report in patients with Kufs disease.

CONCLUSIONS

Gene analysis results of the first patient revealed a homozygous mutation c231C > G, p.Asn77Lys in exon 3 and a homozygous c.297 + 48 A > T mutation in intron 3 in the CLN6 gene. The Asn amino acid is perfectly conserved among species. In silico analysis showed that the mutation is predicted to be probably damaging. Moreover, the second patient with Kufs disease also had the same homozygous mutations. These data suggest that the missense mutation must be pathogenic. Furthermore, the patients had lived in the same district; therefore, they both potentially inherited the founder effect mutations.

Molecular Characterization of Glucose-6-Phosphate Dehydrogenase Deficiency in the Shenzhen Population

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is caused by one or more mutations in the G6PD gene on chromosome X. This study aimed to characterize the G6PD gene variant distribution in Shenzhen of Guangdong province.

METHODS

A total of 33,562 individuals were selected at the hospital for retrospective analysis, of which 1,213 cases with enzymatic activity-confirmed G6PD deficiency were screened for G6PD gene variants. Amplification refractory mutation system PCR was first used to screen the 6 dominant mutants in the Chinese population (c.1376G>T, c.1388G>A, c.95A>G, c.1024C>T, c.392G>T, and c.871G>A). If the 6 hotspot variants were not found, next-generation sequencing was then performed. Finally, Sanger sequencing was used to verify all the mutations.

RESULTS

The incidence of G6PD deficiency in this study was 3.54%. A total of 26 kinds of mutants were found in the coding region, except for c.-8-624T>C, which was in the noncoding region. c.1376G>T and c.1388G>A, both located in exon 12, were the top 2 mutants, accounting for 68.43% of all individuals. The 6 hotspot mutations had a cumulative proportion of 94.02%.

CONCLUSIONS

This study provided detailed characteristics of G6PD gene variants in Shenzhen, and the results would be valuable to enrich the knowledge of G6PD deficiency.

Glucose-6-phosphate dehydrogenase mutations in malaria endemic area of Thailand by multiplexed high-resolution melting curve analysis

Background

Glucose-6-phosphate dehydrogenase (G6PD) deficiency, the most common enzymopathy in humans, is prevalent in tropical and subtropical areas where malaria is endemic. Anti-malarial drugs, such as primaquine and tafenoquine, can cause haemolysis in G6PD-deficient individuals. Hence, G6PD testing is recommended before radical treatment against vivax malaria. Phenotypic assays have been widely used for screening G6PD deficiency, but in heterozygous females, the random lyonization causes difficulty in interpreting the results. Over 200 G6PD variants have been identified, which form genotypes associated with differences in the degree of G6PD deficiency and vulnerability to haemolysis. This study aimed to assess the frequency of G6PD mutations using a newly developed molecular genotyping test.

Methods

A multiplexed high-resolution melting (HRM) assay was developed to detect eight G6PD mutations, in which four mutations can be tested simultaneously. Validation of the method was performed using 70 G6PD-deficient samples. The test was then applied to screen 725 blood samples from people living along the Thai–Myanmar border. The enzyme activity of these samples was also determined using water-soluble tetrazolium salts (WST-8) assay. Then, the correlation between genotype and enzyme activity was analysed.

Results

The sensitivity of the multiplexed HRM assay for detecting G6PD mutations was 100 % [95 % confidence interval (CI): 94.87–100 %] with specificity of 100 % (95 % CI: 87.66–100 %). The overall prevalence of G6PD deficiency in the studied population as revealed by phenotypic WST-8 assay was 20.55 % (149/725). In contrast, by the multiplexed HRM assay, 27.17 % (197/725) of subjects were shown to have G6PD mutations. The mutations detected in this study included four single variants, G6PD Mahidol (187/197), G6PD Canton (4/197), G6PD Viangchan (3/197) and G6PD Chinese-5 (1/197), and two double mutations, G6PD Mahidol + Canton (1/197) and G6PD Chinese-4 + Viangchan (1/197). A broad range of G6PD enzyme activities were observed in individuals carrying G6PD Mahidol, especially in females.

Conclusions

The multiplexed HRM-based assay is sensitive and reliable for detecting G6PD mutations. This genotyping assay can facilitate the detection of heterozygotes, which could be useful as a supplementary approach for high-throughput screening of G6PD deficiency in malaria endemic areas before the administration of primaquine and tafenoquine.

Rapid detection of twenty-nine common Chinese glucose-6-phosphate dehydrogenase variants using a matrix-assisted laser desorption/ionization-time of flight mass spectrometry assay on dried blood spots

BACKGROUND

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common inherited disease. Current neonatal screening methods for G6PD deficiency primarily rely on the use of biochemical tests. However, only 15%-20% of female carriers were estimated to have been detected using these tests. As a better alternative, DNA-based tests could be used for G6PD deficiency screening. We aimed to develop a matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) assay for G6PD variant detection.

METHODS

A MALDI-TOF MS assay with multiprimer extension (multi-PEX) was developed to rapidly and accurately detect the 29 common G6PD variants in the Chinese population using a dried blood spot as a template. A parallel study screening 571 unrelated neonatal samples using the MALDI-TOF MS and fluorescence quantitative enzymatic assays was performed. All results were confirmed by Sanger sequencing in a blind study.

RESULTS

In 571 unrelated neonatal samples, 34 positive samples, including 26 samples from hemizygous males and eight samples from heterozygous females, were correctly identified, yielding a clinical sensitivity of 100%. The results were validated using Sanger sequencing with 100% concordance. In contrast, the fluorescence quantitative enzymatic assay had a 75% false negative and 88.8% false positive rate for the detection of heterozygous G6PD deficient females.

CONCLUSIONS

We established a reliable MALDI-TOF MS assay for G6PD deficiency screening in the Chinese population maximizing the chance of detection of heterozygous G6PD deficient females and reducing the false negative and false positive rates associated with routinely used newborn screening procedures.

Applying a multiplexed primer extension method on dried blood spots increased the detection of carriers at risk of glucose-6-phosphate dehydrogenase deficiency in newborn screening program

BACKGROUND

Patients with glucose-6-phosphate dehydrogenase deficiency might develop acute hemolytic anemia, chronic hemolytic anemia, and neonatal hyperbilirubinemia when exposed to high levels of oxidative stress. Severe hemolysis may occur in not only patients but also female carriers under certain conditions. However, 80%-85% of female carriers were undetected in an existing newborn screening program because of their wide-ranging levels of enzyme activity.

METHODS

We developed a cost- and time-efficient multiplex SNaPshot assay using dried blood spots.

RESULTS

By detecting 21 common mutations in Taiwan and Southeast Asia, the assay could determine 98.2% of the mutant alleles in our cohort of Taiwanese newborns. The 9 undetermined mutant alleles were consequently detected by Sanger sequencing, of which 5 unpublished variations-c.187G > A (Pingtung), c.585G > C (Tainan), c.586A > T (Changhua), c.743G > A (Chiayi), and c.1330G > A (Tainan-2)-were detected. Furthermore, 13% of mild mutations were missed in male infants whose enzyme levels at 6.1-7.0 U/gHb in the newborn screening program when set the cutoff value at 6.0 U/gHb. We therefore suggest increasing the cutoff value and applying the multiplex SNaPshot assay as the second tier for neonatal screening.

CONCLUSIONS

Our approach could significantly increase the detection rate of male patients and female carriers with a reasonable cost and a reasonable number of clinic referrals.

STARD-rapid screening for the 6 most common G6PD gene mutations in the Chinese population using the amplification refractory mutation system combined with melting curve analysis

Dot-blot hybridization and high-resolution melting curve methods are used to detect G6PD gene mutations; however, the performance and throughput limitations of these methods hinder their use for screening large populations. For simple screening, we developed a novel approach called "Amplification Refractory Mutation System combined with Melting Curve Analysis (ARMS-MC)," which enables rapid and batch-based detection of the 6 most common G6PD mutations.In this method, we established 4 PCR reaction systems that can be used to detect the 6 most common G6PD mutations (c.95A>G, c.392G>T, c.871G>A, c.1024C>T, c.1376G>T, and c.1388G>A) in the Chinese population.The ARMS-MC method was evaluated with 174 cases of clinical G6PD-deficient samples, and the results were verified by direct sequencing at G6PD gene exons. The results showed that 170 samples had ≥1 of the 6 mutations, which accounted for 97.70% of all mutations. These results were consistent with the results of direct sequencing with 100% accuracy and specificity. Sequencing validation revealed other mutations in the 4 samples in which no mutation was detected by the ARMS-MC method.ARMS-MC provides a rapid, simple, inexpensive, and accurate screening method for detecting the most common G6PD mutations in Chinese people.

Rapid detection of G6PD mutations by multicolor melting curve analysis

The MeltPro G6PD assay is the first commercial genetic test for glucose-6-phosphate dehydrogenase (G6PD) deficiency. This multicolor melting curve analysis-based real-time PCR assay is designed to genotype 16 G6PD mutations prevalent in the Chinese population. We comprehensively evaluated both the analytical and clinical performances of this assay. All 16 mutations were accurately genotyped, and the standard deviation of the measured Tm was <0.3°C. The limit of detection was 1.0ng/μL human genomic DNA. The assay could be run on four mainstream models of real-time PCR machines. The shortest running time (150min) was obtained with LightCycler 480 II. A clinical study using 763 samples collected from three hospitals indicated that, of 433 samples with reduced G6PD activity, the MeltPro assay identified 423 samples as mutant, yielding a clinical sensitivity of 97.7% (423/433). Of the 117 male samples with normal G6PD activity, the MeltPro assay confirmed that 116 samples were wild type, yielding a clinical specificity of 99.1% (116/117). Moreover, the MeltPro assay demonstrated 100% concordance with DNA sequencing for all targeted mutations. We concluded that the MeltPro G6PD assay is useful as a diagnostic or screening tool for G6PD deficiency in clinical settings.

A multiplex method for detection of glucose-6-phosphate dehydrogenase (G6PD) gene mutations

INTRODUCTION

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common human enzyme defect caused by G6PD gene mutations. This study aimed to develop a cost-effective, multiplex, genotyping method for detecting common mutations in the G6PD gene.

METHODS

We used a SNaPshot approach to genotype multiple G6PD mutations that are common to human populations in South-East Asia. This assay is based on multiplex PCR coupled with primer extension reactions. Different G6PD gene mutations were determined by peak retention time and colors of the primer extension products.

RESULTS

We designed PCR primers for multiplex amplification of the G6PD gene fragments and for primer extension reactions to genotype 11 G6PD mutations. DNA samples from a total of 120 unrelated G6PD-deficient individuals from the China-Myanmar border area were used to establish and validate this method. Direct sequencing of the PCR products demonstrated 100% concordance between the SNaPshot and the sequencing results.

CONCLUSION

The SNaPshot method offers a specific and sensitive alternative for simultaneously interrogating multiple G6PD mutations.

Glucose-6-phosphate dehydrogenase deficiency in Italian blood donors: prevalence and molecular defect characterization

BACKGROUND

In the countries with high G6PD deficiency prevalence, blood donors are not routinely screened for this genetic defect. G6PD deficiency is often asymptomatic, blood donors may be carriers of the deficiency without being aware of it. The aim of the study was to evaluate the prevalence of G6PD deficiency among the Italian blood donors.

DESIGN AND METHODS

From October 2009 to April 2011, 3004 blood donors from a large hospital transfusion centre were screened for G6PD deficiency using differential pH-metry and the characterization of G6PD mutations was performed on G6PD-deficient subjects. The haematological features of G6PD-deficient and normal donors were also compared.

RESULTS

Thirty-three subjects (25 men and 8 women) with low G6PD activity were identified, corresponding to 1·1% of the examined blood donor population. The frequencies of class II severe alleles (Mediterranean, Valladolid, Chatham and Cassano) and class III mild alleles (Seattle, A- and Neapolis) were 48% and 43%, respectively. The haematological parameters of G6PD- donors were within normal range; however, the comparison between normal and G6PD- class II donors showed significant differences.

CONCLUSION

In Italy, the presence of blood donors with G6PD deficiency is not a rare event and the class II severe variants are frequent. The identification of G6PD-deficient donors and the characterization of the molecular variants would prevent the use of G6PD-deficient RBC units when the haemolytic complications could be relevant especially for high risk patients as premature infants and neonates and patients with sickle cell disease submitted to multiple transfusions.

Three new mutations account for the prevalence of glucose 6 phosphate deshydrogenase (G6PD) deficiency in Tunisia

A previous study on G6PD deficiency carried out on Tunisian population, led to the finding of seven different mutations with the prevalence of G6PD A- variant. This present study reports 23 new unrelated deficient subjects studied at the molecular level to determine the mutation that causes G6PD deficiency. Using PCR-SSCP of coding regions followed by direct sequencing of abnormal pattern, three new mutations were detected. Two of them are polymorphic intronic mutations. The first is IVS-V 655C-->C/T, found in four female subjects with mild deficiency of class III variant. The second is IVS-VIII 43 G-->A, found in three male subjects with mild deficiency of class III variant. The third mutation is in the exon region so that it changes the primary structure of the molecule. It is cited for the first time and named G6PD Tunisia. This variant affects the exon 7 of the gene at genomic position 15435 G→T. Its cDNA position is 93 G→G/T, it changes arg 246 to leu. This mutation was found in one heterozygote female with deficiency of class II who have had hemolytic anemia due to ingestion of fava beans. Finally, G6PD Med variant, reported before in three cases, was also found in five other cases (four heterozygote females and one male hemizygote). These findings first enlarge the spectre of mutations to be ten variant mutations, characterizing the Tunisian population and also contribute with hemoglobin gene research in our laboratory to trace the whole genetic map of Tunisian population.

Correlation between AVPR2 mutations and urinary AQP2 excretion in patients with nephrogenic diabetes insipidus

Activation of the V2 receptor by arginine vasopressin (AVP) results in trafficking of the water channel AQP2 to the luminal plasma membrane and a small amount into the urine. Mutations in the A VPR2 gene, encoding the AVP V2 receptor, result in congenital nephrogenic diabetes insipidus (CNDI). To determine a correlation between A VPR2 mutations and urinary AQP2 excretion, immunobloting was used to detect AQP2 in the urine of patients with CNDI before and after a dehydration test. The patients' genotype was determined using PCR amplification and direct sequencing of the complete A VPR2 gene. Urinary AQP2 excretion was absent in patients with severely debilitating mutations, a novel total deletion of the A VPR2 gene, and a novel nonsense mutation W296X. However, it was detected in siblings with a V88M missense mutation. Urinary AQP2 excretion correlated well with other tested phenotype markers. Urinary AQP2 excretion could be used to evaluate the remaining in vivo integrity of the AVP-V2 receptor-AQP2 cascade in patients with CNDI.

Glucose-6-phosphate dehydrogenase variants associated with favism in Thai children

In a study conducted at Songklanagarind Hospital in the south of Thailand, the subjects were 225 patients (210 boys and 15 girls) with glucose-6-phosphate dehydrogenase (G6PD) deficiency. Favism was found in 3.6% of the G6PD-deficient children. Approximately one half of the G6PD-deficient patients with favism were younger than 2 years. Sudden onset of anemia was found within 1 to 3 days after ingestion of dried fava beans. The classic features of favism, which are pallor, hemoglobinuria, and jaundice, were detected in all cases. To characterize the known G6PD mutations in Thai children, molecular analysis was performed for 8 G6PD-deficient children with favism by a combination of polymerase chain reaction-restriction fragment length polymorphism analysis and amplification refractory mutation system analysis. The G6PD variants in these children were G6PD Kaiping 1388,G-->A; G6PD Mahidol 487,G-->A; G6PD Viangchan 871,G-->A; and uncharacterized mutation with silent mutation 1311,C-->T.