Prenatal diagnosis of Huntington disease in maternal plasma: direct and indirect study.

BACKGROUND AND PURPOSE: The presence of cell-free fetal DNA in maternal plasma could allow performing a non-invasive prenatal diagnosis of Huntington disease (HD). The great advantage of this diagnosis is the absence of risk of fetal loss that it entails.

METHODS

Maternal plasma from four pregnant women in their first trimester of gestation with a fetus at-risk was studied. In all the four cases, the father was affected.

RESULTS

The diagnosis was performed both by a direct study of the mutation and an indirect haplotype study. By the direct analysis, three out of the four fetuses could be correctly diagnosed whilst the indirect analysis was only conclusive in one case.

CONCLUSIONS

Non-invasive prenatal diagnosis of HD is possible by the analysis of fetal DNA in maternal plasma. Direct analysis of the mutation has shown higher accuracy than the haplotype analysis except for long expansions. Haplotype analysis would need to be improved for the study of Juvenile-onset HD. This diagnostic method would be limited to those couples with an affected male however this situation represents 80-90% of the pregnancies at-risk of HD. Moreover, it could be used as a confirmation test of healthy embryos transferred on pre-implantation genetic studies of HD.