Genotype and phenotype of haemophilia A in Thai patients.

To study genotype and phenotype correlation of haemophilia A in Thai patients, molecular defects of the factor VIII (FVIII) gene were examined and their correlation with clinical phenotypes were evaluated. The molecular pathologies of FVIII in Thai patients were found to be heterogeneous. The most common mutation was FVIII intron 22 inversion accounting for about 30% of the severe cases while gene deletion was rare. Sixteen point mutations were identified, comprising two nonsense mutations (R-5X and R1966X), five missense mutations (T233I, D542Y, G1850V, W2229S and G2325C), five nucleotide deletions (1145delT, 1187-8delACAC, 1191-4delA, 1458delGA and 1534delA), three nucleotide insertions (1439-41insA, 1934insTA and 2245insACTA) and one splicing defect (IVS15+1G>T). Nine mutations (T233I, D542Y, 1145delT, 1458delGA, 1534delA, 1934insTA, W2229S, 2245insACTA and G2325C) were novel, firstly identified in Thai patients. The genotypes were found to correlate with clinical phenotypes in a majority of cases. However, in five patients the molecular defects did not correlate with clinical severity and FVIII:C level. Cellular and molecular mechanisms were proposed to be responsible in amelioration of clinical severity caused by deleterious mutations. Carrier detection by direct mutation analysis was also demonstrated.

Mutation causing exon 15 skipping and partial exon 16 deletion in factor VIII transcript, and a method for direct mutation detection.

A splicing defect with 201 nucleotide deletion in the factor VIII transcript due to IVS15 + 1G > T mutation inactivating this donor splice site and activating a cryptic acceptor splice site in exon 16 was identified in a severe haemophilia A patient. Allele specific amplification (ASA) method was successfully developed for direct detection of this mutation.

Determination of haemophilia A carrier status by mutation analysis.

A reliable method for determination of carrier status and genetic counselling is required for effective control of haemophilia. Linkage analysis is currently the most widely used method for this purpose; however, in cases where there is no prior family history and/or unavailability of informative polymorphic markers it is less applicable. Detection of a mutation characterized in each family may be an alternative method for determination of the carrier status. In this study, linkage analysis using four polymorphic DNA markers, and direct mutation analysis were compared to determine the carrier status in six unrelated Thai haemophilia A families, two with a family history and four without. In the two families with a family history of haemophilia A, the carrier and noncarrier statuses could readily be determined in eight females by either linkage or direct mutation analysis. In the four families without a family history, the polymorphic DNA markers for linkage analysis were informative in two families and uninformative in the other two. The carrier status could be excluded in all four female siblings of the patients in the former. However, the specific FVIII gene mutation was not observed in the mother of one patient, who should have carried the mutation. In the remaining two families with uninformative polymorphic DNA markers, the carrier and noncarrier statuses of four female members could only be determined by direct mutation analysis. Therefore, direct mutation analysis could circumvent the limitations of linkage analysis in the determination of haemophilia A carrier status in families without a previous history or informative polymorphic markers.

Linear growth in homozygous beta-thalassemia and beta-thalassemia/hemoglobin E patients under different treatment regimens.

The effects on linear growth and development among thalassemic patients under different treatment regimens were compared. Twelve homozygous beta-thalassemia (homozygous beta-thal) and 36 beta-thalassemia/Hb E (beta-thal/Hb E) were studied longitudinally between 1977 and 1998. Eighteen cases (10 homozygous beta-thal and 8 beta-thal/Hb E) received hypertransfusion with iron chelation by desferrioxamine. Another 30 cases (2 homozygous beta-thal and 28 beta-thal/Hb E) were given a low transfusion (depending on their clinical requirement). Their heights were measured serially and are presented as a standard deviation score (SDS). There was no significant difference in initial basic hematological data and ferritin levels between either group. However, the hypertransfused group, seemed to be clinically more severely affected than the other group as evidenced by early age at initial transfusion, the early onset of anemia and diagnosis and also their large acquired iron load after a period of transfusion. The average height SDS of the hypertransfused patients was within the 50th percentile +/- 1 SD during the first decade of life in both sexes and both genotypes. Whereas, in patients who were transfused infrequently, the SDS was always below the -1 SD and decreased gradually. In severe beta-thal/Hb E cases, their growth SDS showed no difference from those with homozygous beta-thal. Normal linear growth in those with homozygous beta thal and severe beta-thal/Hb E was only seen in the group that underwent hypertransfusion and this regimen contributed to normal growth during the first ten years of life. However, adequate iron chelation and hormonal treatment in these patients were also required in order to achieve normal adult height.

Frameshift mutations with severe and moderate clinical phenotypes in Thai hemophilia A patients.

Six frameshift mutations in exon 14 of the factor VIII gene were identified in Thai hemophilia A patients. Although all these mutations created premature stop codons and expected to cause severe disease, the molecular defects and clinical severity were in discrepancy in some patients. Four mutations (delT3490, delACAC3618-21, delGA4429-30, and delA4658) were found in the patients with the severe clinical phenotype while two (delA3629-37 and insA4372-9) were observed in the patients who had moderate severity, with FVIII:C of 4.2 and 2.8%. The frameshift mutations in these two patients were due to deletion and insertion of an 'A' nucleotide in the stretches of 9As and 8As in codons 1191-4 and 1439-41, respectively. This indicates that deletion or insertion in the stretches of poly A nucleotides in exon 14 of the factor VIII gene is a likely cause of the moderate clinical severity in some cases of Thai hemophilia A patients.

Mutations of the factor VIII gene in thai hemophilia A patients.

Hemophilia A is a common X-linked bleeding disorder caused by mutations in the coagulation factor VIII gene. The entire coding and essential sequences of the factor VIII gene were generated by a combination of genomic DNA amplification and long reverse transcription-polymerase chain reaction (long RT-PCR) using factor VIII transcripts prepared from lymphocytes. Mutations were then screened by non-radioactive single strand conformation polymorphism (SSCP) analysis and characterized by DNA sequencing. We have identified six potentially pathogenic mutations in the factor VIII gene in Thai hemophilia A patients, including two nonsense mutations (R-5X and R1966X), three missense mutations (D542Y, G1850V, and G2325C), and a 4-bp insertion (ACTA) at codon 2245. Three of these mutations (D542Y, G2325C, and 4-bp insertion) have never been previously reported, and the ins2245 is the first example of such insertion probably causing factor VIII elongation. R1966X, D542Y, G1850V, and 4-bp insertion were associated with a severe hemophiliac phenotype whereas R-5X and G2325C were observed in moderately affected patients. Mutations in the factor VIII gene in Thai hemophilia A patients are likely to be heterogeneous. This study represents the first attempt to further the understanding of the molecular basis of hemophilia A in Thai.

Compound heterozygosity for one novel and one recurrent mutation in a Thai patient with severe protein S deficiency.

Homozygous or compound heterozygous protein S (PS) deficiency is a very rare disorder in the anticoagulant system, that can lead to life-threatening thrombotic complications shortly after birth. This report describes the results of the genetic analysis of the PROS 1 genes in a Thai girl patient. She was reported in 1990 as the first case with homozygous PS deficiency and neonatal purpura fulminans. In the present report, we identified the mutations in this patient by direct sequencing of PCR products representing all 15 exons of the PROS 1 gene and their flanking intronic regions. The patient turned out to be compound heterozygous for two null mutations. One allele contained a novel sequence variation, an A-insertion in an A5-tract covering codon 146 and 147, that results in a frameshift and a stop codon (TAA) at position 155. The other allele contained a nonsense mutation in exon 12 by a transition at codon 410 CGA (Arg) to TGA (stop). Cosegregation of PS deficiency with these two genetic defects was observed in her family.

Prevalence of HB E from cord blood samples and after one year follow-up.

Hemoglobin (Hb) E is the most prevalent hemoglobinopathy in Southeast Asia. The prevalence of this condition varies from 9-60% of the population in different regions of Thailand and has the highest prevalence the northeast of the country. Neonatal diagnosis of Hb E can be made by detecting the Hb band in cord blood samples at the Hb A2 position using starch gel and cellulose acetate electrophoresis. Our study, performed in Bangkok, in the central part of Thailand, resealed that 182 out of 1,015 cord blood samples (17.9%) contained Hb E in amounts of between 1.9 and 10.0%. The cases who had Hb A, F and E with or without Hb Bart's were initially included in the study. These cases were suspected to have the Hb E trait. One hundred and seven cases (58.89%) were available for follow up and in all of these, Hb E could be detected throughout the study. A sharp increase in the amount of Hb E was observed at the 3 months follow-up appointment. One year follow-up could be made in 72 cases (39.6%) when the percentage of Hb E was around 25%. We conclude that measurement of Hb E in cord blood an easily accessible, simple, practical and sensitive procedure which can be used to study the Hb E hemoglobinopathy which is widely distributed in Thailand and Southeast Asia.

A novel Asn344 deletion in the core domain of coagulation factor XIII A subunit: its effects on protein structure and function.

In this study a previously undescribed 3 bp deletion, AAT1030-1032, in the factor XIII A subunit gene, has been detected in a Thai patient. The inframe deletion results in the translation of a factor XIII A subunit that lacks Asn344. This is the first inframe deletion to be identified in the factor XIII A subunit gene because six previously reported deletions have all caused frameshifts. The deletion has been introduced into a factor XIII A subunit cDNA and the deleted polypeptide expressed in yeast. The mRNA encoding the mutant enzyme appears to have normal stability but the translated protein is subject to premature degradation. In addition, the mutated enzyme exhibited very little transglutaminase activity compared with the wild-type enzyme. Structural modeling of the deleted enzyme suggests that the absence of Asn344 would have a potent impact on the catalytic activity by reorienting the residues associated with the catalytic center. Thus, the Asn344 deletion strongly confirms the significance of the residues surrounding the catalytic center of the factor XIII A subunit.

Molecular basis of hereditary methaemoglobinaemia, types I and II: two novel mutations in the NADH-cytochrome b5 reductase gene.

Hereditary methaemoglobinaemia, caused by deficiency of NADH-cytochrome b5 reductase (b5R), has been classified into two types, an erythrocyte (type I) and a generalized (type II). We analysed the b5R gene of two Thai patients and found two novel mutations. The patient with type II was homozygous for a C-to-T substitution in codon 8 3 that changes Arg (CGA) to a stop codon (TGA), resulting in a truncated b5R without the catalytic portion. The patient with type I was homozygous for a C-to-T substitution in codon 178 causing replacement of Ala (GCG) with Val (GTG). To characterize effects of this missense mutation, we investigated enzymatic properties of mutant b5R (Ala 178 Val). Although the mutant enzyme showed normal catalytic activity, less stability and different spectra were observed. These results suggest that this substitution influenced enzyme stability due to the slight change of structure. In conclusion, the nonsense mutation led to type II because of malfunction of the truncated protein. On the other hand, the missense mutation caused type I, due to degradation of the unstable mutant enzyme with normal activities in patient's erythrocytes, because of the lack of compensation by new protein synthesis during the long life-span of erythrocytes.

Pyruvate kinase deficiency in an alpha-thalassemia family: first case report in Thailand.

In Thailand, the most common cause of chronic hemolytic anemia is thalassemia hemoglobinopathy. We report here a 10-year-old girl with pyruvate kinase (PK) deficiency who was initially diagnosed to have Hb H disease, like her sister. The patient had a history of neonatal jaundice which required blood exchange transfusion twice and phototherapy. She became anemic and regular blood transfusion was required since the age of 2 1/2 months. She was very anemic compared to her sister and was transfusion dependent. Besides, she never had red cell inclusion bodies, thus re-evaluation was performed. The diagnosis of red cell pyruvate kinase deficiency and the exclusion of Hb H disease was achieved after cessation of blood transfusion for 3 months. The family study also confirmed the diagnosis. The patient is now on high transfusion and iron chelation. She is doing well with mild splenomegaly.

Glucose-6-phosphate dehydrogenase deficiency in the newborn: its prevalence and relation to neonatal jaundice.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is prevalent in Thailand. This condition can cause acute hemolysis during oxidative stress and also severe hyperbilirubinemia in the newborn in some populations. Our aim was to study the prevalence of G6PD deficiency in relation to neonatal jaundice. We performed quantitative red blood cell (RBC) G6PD assay in the cord blood of 505 male subjects. Observation of jaundice and determination of bilirubin level as well as work up for other causes of jaundice were made in the G6PD deficiency group compared to a G6PD normal group. Questionnaires were also sent for further follow up to both groups. The results of the study were as follows: Sixty-one of 505 male (12.08%) had RBC G6PD deficiency (Group I). The rest (444 cases) had normal G6PD (Group II). In Group I, 49.15% developed neonatal jaundice, of which 28.82% were physiologic and 20.33% were pathologic jaundice. In group II, 23.68% developed jaundice; 16.51% were physiologic and 7.17% were pathologic jaundice, respectively. Onset of jaundice, date of peak bilirubin and peak bilirubin level in Group I and Group II were not statistically different. ABO incompatibility was associated with Group I in 17.24% and with Group II in 9.09%. Hospitalization day in Groups I and II were not statistically different. Other associated diseases were found in both groups, ie infection, congenital malformation, respiratory distress syndrome, but there was no significant difference in terms of jaundice. Phototherapy was required in 18.64% and 10.28% in Group I and II with a duration of 3.91 +/- 1.24 and 3.21 +/- 1.75 days, respectively. One case in Group I who was also premature received one exchange blood transfusion due to severe sepsis but he did not survive. One case in Group II who had polycythemia was successfully treated by partial exchange transfusion with plasma.

Prevalence of hemoglobin E, alpha-thalassemia and glucose-6-phosphate dehydrogenase deficiency in 1,000 cord bloods studied in Bangkok.

Thalassemia hemoglobinopathies and glucose-6-phosphate dehydrogenase (G-6-PD) deficiency are prevalent in Thailand. We studied the prevalence of these disorders from 1,000 cord bloods collected during 14 months period, using EDTA as anticoagulant. Red blood cell G-6-PD quantitative assay was performed in all male subjects. Nine hundred and eighty five specimens were available for hemoglobin (Hb) typing by starch gel electrophoresis. Further evaluation by cellulose acetate electrophoresis and follow up were made in the cases who had Hb E and/or high level of Hb Bart's. It was found that out of 505 males, 61 cases (12.08%) had G-6-PD deficiency. Among 985 cases studied for Hb typing, 61.92% revealed normal Hb type AF while Hb E was present in 18.68% and Hb Bart's designated alpha-thalassemias were present in 25.18% respectively. Of these 985 cases, 18.78% had low Hb Bart's level ie detectable to 8.2% consistent with alpha-thal2, Hb Constant Spring (CS) or alpha-thal1 trait. Ten cases (1.02%) had high levels of Hb Bart's ranging from 16.1-35% without or with Hb CS and E, and further follow-up revealed homozygous Hb CS, Hb A-E-Bart's, Hb H and Hb H with Hb CS disease. The other 53 cases (5.38%) had low level of Hb Bart's with Hb E consistent with alpha-thalassemia trait with Hb E trait. There were 127 cases (12.89%) who had only Hb E trait and 3 cases (0.3%) who had Hb F and E without Hb A initially.

Evidence of vitamin K deficiency in cord blood.

The prevalence of vitamin K deficiency in the newborns delivered at Siriraj Hospital was studied. The prolongation of one stage prothrombin time and the presence of PIVKA-II (non carboxylated prothrombin antigen) in cord blood were interpreted as the secondary change from vitamin K deficiency state. The most reliable method to diagnose vitamin K deficiency is the detection of vitamin K level in plasma which is not yet available in Thailand. Although the prevalence of vitamin K deficiency in the newborns from our data is not high, only 0.6%, it is shown that some of the apparently normal newborn infants may have bleeding problem from vitamin K deficiency in both newborn and early infancy periods. So, the correction of this deficiency by administration of vitamin K to all newborns is appropriate and reasonable decision.

Hemoglobin constant spring in Bangkok: molecular screening by selective enzymatic amplification of the alpha 2-globin gene.

Hemoglobin Constant Spring (Hb CS) is a hemoglobin variant with an elongated alpha-globin chain secondary to a chain termination mutation. The diagnosis of HbCS by electrophoresis is difficult because it is present in very low amounts in the red cells of heterozygotes. Selective enzymatic amplification of the alpha 2-globin gene and allele-specific hybridization for Hb CS gene provided accurate diagnosis of Hb Constant Spring. We have used this approach to detect the alpha cs mutation in the cord blood that contained all four alpha-globin genes but had Hb Bart on electrophoresis. The alpha cs mutation was found in six subjects whose Hb Bart levels were 3.0, 3.2, 3.7, 4.0, 4.9, and 9.8%. The latter also had -alpha mutation on the other chromosome, giving rise to the genotype alpha cs alpha/-alpha, which produced high Hb Bart. The gene frequency for alpha cs in the Thai calculated from a total of 406 cord blood studied in Bangkok was found to be approximately 0.008.