Genetic Screening in Women at Risk of Duchenne, Becker Muscular Dystrophies Could Aid Prenatal Diagnosis, Study Shows
Genetic screening for the presence of mutations that characterize Duchenne and Becker muscular dystrophies (DMD and BMD) in women before conception can help determine the risk their offspring will develop either disease, according to a Polish study published in the Journal of Obstetrics Gynaecology Research.
The study, “Prenatal diagnosis of Duchenne and Becker muscular dystrophies: Underestimated problem of the secondary prevention of monogenetic disorders,” says such tests can help early diagnosis and future care planning for the children of affected families.
Researchers at Warsaw’s Institute of Psychiatry and Neurology performed genetic prenatal tests on 169 Polish women. These included 78 women identified as D/BMD carriers and 23 as non-carriers but mothers of children with DMD or BMD. The remaining 68 were at risk of D/BMD (uncertain carrier status). The team performed 201 genetic prenatal tests on this group between January 1992 and June 2012.
“The majority of tested women have already had affected children, which confirms the hypothesis that ‘learning with life’ has a stronger impact on reproductive decisions than genetic counseling,” the study’s authors wrote.
Among these women, 52.7 percent were tested for carrier status before conception. Tests in male fetuses, in pregnancies of confirmed carriers and non-carriers, were all conclusive. On the other hand, in women with uncertain carrier status, only 60 percent of the tests performed in male fetuses returned conclusive results. In addition, 85 out of 103 female fetuses were tested, and only 31.8 only had a confirmed D/BMD carrier status.
According to the authors, these results suggest that testing women for determination of their carrier status prior to conception can help decrease the number of unnecessary and invasive prenatal procedures in non-carriers.
“In mothers of affected children, prenatal testing is recommended in all subsequent pregnancies,” they wrote. “Prenatal testing of D/BMD carrier status as well as genetic testing of female minors is controversial, as no health benefits in childhood have been shown in the majority of tested female minors.”
DMD and BMD are caused by genetic mutations that occur in a gene located in the X chromosome, which encodes the protein dystrophin. These mutations can lead to total loss of the protein, causing DMD, or can produce an abnormal form of the protein, which leads to BMD, a more mild form of Duchenne.
Because women have two X chromosomes, they are commonly asymptomatic carriers of the genetic defect, passing it to their offspring. Once the sex of the fetus is known, it is possible to genetically screen for the presence of genetic mutations in dystrophin gene, and find out if it will have or won’t have the diseases. However, this methodology is still controversial and involves possible health risks.
D/BMD carriers not only risk having affected offspring, but also developing serious cardiac illnesses. For this reason, authors said, physicians should conduct cardiac screens for early detection of heart involvement in these female carriers.