Genetic Diagnosis Of Haemophilia Research Articles

Factor VIII mutation spectrum in haemophilia A patients in the population of Henan, China.

: Defects in the coagulation factor VIII gene cause haemophilia A, which is the most common X-linked recessive bleeding disorder. In total, 45 affected families were investigated to elucidate the factor VIII gene mutation spectrum. The families were subjected to clinical, biochemical, and molecular analyses. Inverse-shifting PCR was first applied to severe haemophilia A patients to identify inversions in introns 22 and 1. Then, next-generation sequencing was performed to detect mutations in inversion-negative patients with severe haemophilia A and moderate-mild haemophilia A patients. Finally, multiplex ligation-dependent probe amplification was utilized to identify rare cases with large fragment duplications or deletions in the factor VIII gene. In total, 41 mutations were identified, 19 of which (c.24C>A, c.49T>C, c.170_171delTT, c.533T>C, c.1126delG, c.1495delA, c.1660A>C, c.1736A>G, c.2711-2712insAATCT, c.3077C>G, c.3846delA, c.4238C>G, c.4349delG, c.4828G>C, c.5821A>C, c.6190C>T, c.6656T>C, c.6902T>G, and c.1904-2A>T) were novel and 80% (44/55) of the pathogenic mutations fell into the categories of missense (43.6%), nonsense (16.36%), frameshift (14.55%), and splice (5.45%) mutations. Additionally, 10 (18.18%) patients displayed inversions in intron 22 or 1 and one case (1.82%) exhibited a 3059-bp large fragment deletion in factor VIII. This study aimed to provide insight contributing to the genetic diagnosis of haemophilia A and to fill gaps in the factor VIII mutation spectrum in northern China.

Genetic counseling of hemophilia carriers.

Basic analysis of a potential carrier includes calculation of the probability, or odds, for carriership based on pedigree and clotting factor analysis. Genotype assessment constitutes a more accurate method of carrier detection. Where circumstances permit, the genetic diagnosis of hemophilia should be based on the direct identification of the pathogenic mutation in the factor (F) VIII gene. Neutral mutations in the FVIII gene and the risk of mosaicism (a mixture of normal and mutation carrying cells) in sporadic families may cause misclassification. If it is not possible to use the mutation for diagnostic purposes, it may be possible to use linked polymorphic markers (restriction fragment length polymorphisms [RFLP]) to trace the inheritance of the hemophilia gene within a pedigree. Linkage analysis is limited because of uninformative patterns of polymorphic markers, ethnic variation, linkage disequilibrium, and the need for participation of family members, and it is not useful in sporadic families, which constitute more than half of the hemophilia families. Potential carriers of hemophilia should be offered qualified assistance in genetic information, testing, and counseling to help them to cope with the psychological and ethical problems related to carriership of a genetic disorder.

Genetic diagnosis of haemophilia A of Chinese origin

Genetic diagnosis of haemophilia A has been studied in two aspects. One is to directly identify the mutations in the factor VIII genes of the affected probands, and the other is to examine the usefulness of several intragenic factor VIII markers for gene tracking. Direct mutational analysis by PCR-SSCP (polymerase chain reaction--single-strand conformation polymorphism) has been accomplished previously in 87 haemophilia A patients, accounting for nearly 10% of cases in Taiwan. Of the 87 cases, 46% were with point mutations, short deletions or insertions, and most of the remaining were with gene inversion readily identified by Southern blotting. Further examination of 112 patients has estimated a 33% incidence for gene inversion in all the patients with haemophilia A, or 37% in severe cases. Since the direct mutational detection described above cannot be used in all Chinese families with haemophilia A, genetic markers were also investigated. The two CA repeat markers located at intron 13 (CA-13) and intron 22 (CA-22), respectively, were amplified and analysed simultaneously. Seven different alleles with 18-24 CAs have been identified for CA-13. Alleles of 20 and 21 CAs are the most common and their population frequency was 0.68 and 0.24, respectively. The CA-22 marker contained a repetition of (GT)n(AG)n as was identified in the white European but not in the Canadian population. Alleles with 25 and 26 GT/AGs account for 18% and 75% of this group of samples, respectively. The expected rate of heterozygosity for either CA markers was 68%, although a value of 57% was observed by haplotype analysis, indicating an association of the two repeat markers. Nevertheless, the study of 62 females showed that with the combined use of CA-13 and CA-22 with BclI, approximately 71% would be informative for these markers. This number may increase to 81% if XbaI polymorphism is added. We propose that a better genetic diagnosis procedure for Chinese individuals would be first to look for the inversion mutation, secondly for one of the intragenic markers, and then at the PCR-SSCP analysis.

Multiplex analysis of two intragenic microsatellite repeat polymorphisms in the genetic diagnosis of haemophilia A.

Use of molecular genetic studies for carrier detection and prenatal diagnosis of haemophilia A will be informative in approximately 75% of kindreds with a prior history of the disorder if previously reported bi-allelic intragenic polymorphisms are used. In this study we report the use of two multi-allelic, microsatellite repeat polymorphisms within the factor VIII gene in genetic testing for this disease. These two, dinucleotide repeat, polymorphisms have been analysed using a multiplex polymerase chain reaction (PCR) protocol, and results can be available within 3 d of receipt of samples. At the intron 13 polymorphic locus we have confirmed the original observation of eight alleles, whilst at the intron 22 locus, in contrast to a preliminary report of this polymorphism, we have seen five alleles. We have analysed 32 families (174 subjects) with the two microsatellite repeat markers and have found that using these two polymorphisms alone, 81% of families are informative for linkage analysis. The intron 13 repeat was informative in 22/31 families tested (71%) and the intron 22 polymorphism was informative in 12/17 families (71%). We have also found that in 11/32 families tested (34%) the microsatellite repeats were the only informative intragenic markers. In view of these observations, we believe that the most effective strategy for initiating haemophilia A genetic testing is to combine the multiplex PCR analysis of the intron 13 and 22 dinucleotide repeats with the PCR analysis of the intron 18 BclI marker. In our population this protocol provided informative results in approximately 88% of families and results can be available within 3 d of receiving the samples for testing.

Genetic diagnosis of hemophilia A.

(1994). Genetic Diagnosis of Hemophilia A. Pediatric Hematology and Oncology: Vol. 11, No. 1, pp. 9-11.