Prenatal Diagnostic Testing for Mitochondrial Diseases May Help Future Parents, UK Study Shows

Researchers studied the prenatal diagnostic services provided in the UK for mitochondrial diseases since 2007. The study entitled “A national perspective on prenatal testing for mitochondrial disease” was published on 19 March, 2014 in the European Journal of Human Genetics.

Mitochondrial diseases, including mitochondrial myopathy, affect >1 in 7,500 live births, leading to progressive physical, developmental and mental disabilities. There is no cure for diseases affecting mitochondrial function and caused by mutations in either nuclear DNA (nDNA) or mitochondrial DNA (mtDNA).

Prenatal diagnostic testing for nDNA and mtDNA mutations, usually requested as a result of having had a previously affected child, intends to provide advice related to disease transmission and prevention to future parents. Prenatal testing in the UK faces an increasing demand for genetic counseling by families affected by mitochondrial disease, and this study sleeked for future testing strategies.

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Researchers  particularly focused on the reasons for testing, mutations investigated, and clinical outcome. Sixty-two prenatal diagnoses (17 mtDNA and 45 nDNA mutations) were made since 2007, mostly from chorionic villus (placental tissue) biopsies normally performed at 11–14 weeks after gestation.

Despite the risk associated with this intervention, no spontaneous miscarriages occurred as a result of prenatal testing in this study. At least 11 cases of mitochondrial disease were prevented following prenatal testing, 3 of which were mtDNA mutations. The impact of mtDNA mutations depends on a phenomenon called heteroplasmy: the co-existence of two or more copies of mtDNA in the same cell. Mitochondrial disease may occur if a certain threshold of mutated mtDNA is exceeded. That was the case in two of the patients who had mtDNA mutations, therefore ending in termination of pregnancy. The rest of the identified mutations were in nDNA and some resulted in termination of the pregnancy, but other pregnancies continued with the birth of affected infants. The outcome of others are unknown, since there is few information regarding the follow-up on children after prenatal diagnosis.

“Information on reproductive options including prenatal diagnosis (CVB or amniocentesis), egg donation and sperm donation, techniques to reduce or prevent transmission (eg, PGD), or adoption as an alternative to pregnancy, should be presented to all families affected by mitochondrial disease to facilitate informed reproductive choices, ” concluded the authors of this study.