The C677T MTHFR gene mutation is not predictive of risk for recurrent fetal loss.

We have investigated the potency of the C677T mutation in the methylene tetrahydrofolate reductase (MTHFR) gene as a genetic risk factor in women with a history of early (12 weeks gestation) recurrent miscarriage (three or more consecutive pregnancy losses). Fifty-seven of the total 173 (32. 9%) patients were heterozygous for the MTHFR mutation, 14/173 (8.1%) were homozygous (allele frequency 0.25). The prevalence of the MTHFR mutation in these women did not differ significantly from that in the control group of parous women with uneventful pregnancies, where 30/67 (44.8%) were heterozygous and 6/67 (9.0%) homozygous for the mutation (allele frequency 0.31; odds ratio for homozygous T/T 0.90, 95% CI 0.30-2.4). There was no association between the trimester of pregnancy loss and MTHFR genotype. We conclude that the C677T MTHFR mutation is not a risk predictor in women with a history of early or late recurrent miscarriage.

Factor V Leiden and fatal pulmonary embolism.

To investigate whether the factor V Leiden mutation increases the risk of fatal pulmonary emboli, we determined the presence of the factor V Leiden mutation in pathology material from two series of autopsies of patients from the Leiden University Hospital, The Netherlands. The first series consisted of consecutive autopsies in which pulmonary emboli were mentioned in the autopsy report; most patients of this series had major underlying disease. The second series consisted of autopsies in patients younger than age 70 in which pulmonary emboli were the sole cause of death and no major acquired risk factor for venous thrombosis was present. Extraction of DNA was done on newly prepared tissue from archival paraffin blocks. In the first series, the presence of factor V Leiden was determined in 44 patients, 1 of whom carried the mutation (2.3 percent; 95% confidence interval 0.06 to 12.0 percent). This prevalence is not different from the general population prevalence in The Netherlands. In the second series, factor V Leiden could be determined in 30 patients of whom 3 carried the mutation (10 percent; 95% confidence interval 2. to 26.5 percent), which would lead to a threefold relative risk. A large number of patients with diverse psychiatric diagnoses was present in the second series (eleven). We conclude that in the presence of severe illness, the factor V Leiden mutation plays no additional role in the development of pulmonary emboli. The relative risk of the very rare fatal pulmonary embolus that is the sole cause of death might also be less than the relative risk for deep-vein thrombosis in carriers of the factor V Leiden mutation.

Characterization of a large chromosomal deletion in the PROS1 gene of a patient with protein S deficiency type I using long PCR.

A long-PCR-based technique was developed to investigate a possible deletion in the protein S gene, PROS1, in a family with type I protein S (PS) deficiency (pedigree PS62). Long-PCR across introns produced an unexpected 2kb PCR product between exon VII and XII not seen in control individuals, in addition to the expected 2.5 kb exon VII-VIII product. This result suggested that a deletion had occurred between exons VII and XII in the PS-deficient family members. All were heterozygous for the deletion, Sequencing of the cloned 2 kb fragment gave the precise location of the breakpoints within introns 7 and 11. Significant similarity existed in both introns to repetitive sequences, e.g. Alu and Mer12, but no significant similarity was evident between the two introns themselves. The technique of long-PCR is simple and more informative than Southern blotting in detecting and characterizing large intragenic deletions.