Exome analysis could become a prenatal diagnostic tool in many cases of suspected skeletal abnormality. This was revealed by a study led by Lyn Chitty of the Great Ormond Street NHS Foundation Trust in London.
Undiagnosed skeletal abnormalities affect about 2-5% of pregnancies. Cytogenetic and microarray prenatal screening can identify about 40%. For other types of anomalies, the diagnosis remains complicated. For this reason, the new study explores the potential of exome sequencing analysis in fetuses and parents.
According to an article published in Genetics Medicine, prenatal analysis of the exome would be able to identify 81% of cases of skeletal dysplasia. If the numbers were confirmed, then there would be a further tool for prenatal diagnosis. In particular, this type of test would be useful in cases of suspected unconfirmed anomalies.
Dr. Chitty's study refers to 19 cases of pregnant British women. The women had undergone invasive prenatal tests, after the ultrasound had identified suspected skeletal dysplasias. Of these, 16 went ahead with sequencing.
The researchers used the Illumina NextSeq500 platform to sequence the parental exome and fetal DNA. In case 12, the parents also sequenced the DNA of the siblings due to the low amount of fetal DNA. Researchers focused on the 240 genes related to skeletal dysplasia. A separate project by the Sanger Institute has confirmed all the results.
In 13 cases, the researchers were able to provide a definitive diagnosis. They uncovered 4 recessive pathologies that the fetus had inherited, 6 dominant de novo variants and 2 pathogenic variants inherited from the mother. The last case was more complex. In the 3 cases left without a certain diagnosis, variants were present whose significance was doubtful.