Molecular diagnosis of hemophilia A and B. Report of five families from Costa Rica

Hemophilia A and B are X-chromosome linked bleeding disorders caused by deficiency of the respective coagulation factor VIII and IX. Affected individuals develop a variable phenotype of hemorrhage caused by a broad range of mutations within the Factor VIII or Factor IX gene. Here, were report the results of the molecular diagnosis in a five Costa Rican families affected with Hemophilia. Methods of indirect and direct molecular diagnosis are applied in three Hemophilia A and two Hemophilia B families from Costa Rica as well as preconditions, practicability and facilities of this diagnosis. In two families with Hemophilia A and both families with Hemophilia B the causative mutation could be detected by Southern blotting, polymerase chain reaction or sequence analysis. One Hemophilia A family could only analyzed by linkage analysis using genomic markers.

Carrier detection and prenatal diagnosis in families with haemophilia.

BACKGROUND: Haemophilias are the commonest X-linked disorders affecting approximately 1 in 10,000 male births. Detection of carrier women in families with haemophilia and subsequent antenatal diagnosis of confirmed carriers are important services for these patients and their relatives. Over the last 6 years we performed carrier detection and antenatal diagnosis in families with patients of haemophilia A and B. METHODS: During the last 6 years, 159 families with haemophilia A and B were analysed for carrier detection by DNA analysis, using various polymorphic markers of factors VIII and IX genes. The polymorphisms used were intron 18 Bcl I, intron 19 Hind III, intron 22 Xbal and DXS52/St14 of the factor VIII gene and intron I Ddel, intron 4 Taql, 3 Hhal and Residue 148 codon Mnll of the factor IX gene. There were 189 probable carriers (whose carrier status was not known) and 99 obligatory carriers (confirmed carriers by family pedigree analysis) from 102 families with haemophilia A. Of the 57 families with haemophilia B analysed, there were 98 probable and 52 obligatory carriers. All the analyses were carried out by polymerase chain reaction. For antenatal diagnosis, prior to polymorphism analysis, the sex of the foetus was detected by Y chromosome-specific amplification. RESULTS: One hundred and four females were diagnosed as carriers and 63 as non-carriers by the intragenic polymorphic markers in families with haemophilia A. Eighteen women were informative with only the extragenic marker of factor VIII gene. Four women were not informative with any of the markers used. In families with haemophilia B, 37 women were diagnosed as carriers and 34 as non-carriers by the intragenic markers and 34 were informative only with the extragenic markers. Seventeen women were not informative with any of the markers used. Of the 25 antenatal diagnoses performed (20 haemophilia A, 5 haemophilia B) using the same markers as those used in carrier detection, 14 were male foetuses and 11 female as detected by Y chromosome-specific polymerase chain reaction. Eight were affected males and 6 unaffected. Among the females, 5 were carriers and 6 normal. CONCLUSION: Using the above polymorphic markers of factors VIII and IX genes, a diagnosis could be made in the majority of families.

Detection of carrier status of hemophilia B using DNA markers.

Hemophilia B is an X-linked recessive disorder of the hemostasis involving a defective clotting factor IX. Amplification of the regions containing restriction fragment length polymorphisms (RFLP) can be achieved by the use of polymerase chain reaction (PCR). This paper describes the analysis of 2 RFLPs involving the Dde1 and Taq1 restriction sites within the factor IX gene in a family with hemophilia B. Digestion of the PCR products with Taq1 revealed a 163bp fragment in all the family members. This finding suggests the absence of restriction site for Taq1 enzyme. However, the Dde1 digest results in bands 369bp and 319bp segregated amongst the family members. The pattern of inheritance of the 369bp fragment in this family suggested that both the patient's mother and aunt are not carriers and that the patient's factor IX gene could have undergone a de novo mutation producing a defective factor IX gene responsible for the hemophilia B. This is supported by the fact that no family history of hemophilia B is indicated in the other male members within the family.

DNA polymorphisms for carrier detection of hemophilia in Thailand.

The assessment of carrier state based on the pedigree and laboratory testing in 55 females from 34 Thai hemophilia families (24 affected by hemophilia A, 10 by hemophilia B) was studied. The laboratory testing included phenotypic analysis (FVIII:C/vWF: Ag ratio, FIX:C) and two types of DNA polymorphisms, restriction fragment length polymorphisms (RFLP) and variable number tandem repeats (VNTR) in/and close to the factor VIII genes (Bcl I, Xba I RFLP, St 14 VNTR) and factor IX genes (Mse I, Dde I RFLP). Fifteen out of seventeen (88%) obligate hemophilia A carriers and one out of five (20%) obligate hemophilia B carriers were diagnosed by phenotypic analysis. All hemophilia A carriers were informative for at least one polymorphism (Bcl I, Xba I or St 14) while 42% of hemophilia B carriers were informative for Mse I RFLP only. DNA polymorphism analysis has advantage over phenotypic analysis since it generally gives an absolute diagnosis when informative. Most DNA polymorphism analyses are performed by PCR technique which is a simple, inexpensive and quick procedure. However, it is limited by non-informativeness and high incidence of new mutations.

Molecular analysis of hemophilia B in Brazilian patients

1. The molecular basis of hemophilia B was investigated in 19 Brazilian patients from 14 unrelated families. 2. Southern blotting of TaqI-digested DNA samples was employed for the screening of gene lesions followed by polymerase chain reaction and DNA sequencing for the characterization of mutations. 3. Three different gene mutations were characterized: a nonsense mutation at nucleotide 30875 (codon 252, CGA-->TGA), a partial deletion comprising exons 1-3 (at least 7.4 kb of extension), and a complete deletion (at least 42 kb of extension). These patients are now referred to as Ribeir ao Preto 1, Ribeir ao Preto 2 and Ribeir ao Preto 3, respectively. 4. The factor IX haplotype (composed of 7 polymorphic sites) associated with each mutation was determined. Comparisons with previous studies confirmed an independent origin for the nonsense mutation. 5. This study represents the first survey of gene lesions associated with hemophilia B in South America. The results indicate the presence of heterogeneous mutations, as observed in other populations. These results also contribute to the understanding of the mechanisms involved in the mutations affecting the FIX gene