Prenatal Diagnosis of Myotonic Dystrophy Using Fetal DNA Obtained from Maternal Plasma

Myotonic dystrophy (DM; MIM 160900) is an autosomal dominant disorder associated with expansion of an unstable CTG trinucleotide repeat in the 3′ untranslated region of the DM kinase gene (DMPK) on chromosome 19q13 (1). Patients are heterozygous for expanded alleles in the range of 50–4000 repeats (1). The molecular diagnosis of DM routinely is performed by analyzing the CTG number on genomic DNA extracted from various biological sources, including trophoblast cells sampled at 10–11 weeks of amenorrhea during the first trimester of pregnancy (2)(3). We evaluated the possibility of using maternal plasma for prenatal diagnosis of DM, by monitoring the pregnancy of an unaffected woman whose husband was affected by DM (70 CTG repeats). All participants gave oral and written informed consent. A blood sample (∼10 mL) was collected at 10 weeks of gestation before chorionic villus sampling (CVS) and was centrifuged at 3000 g for 10 min. Plasma was carefully removed from EDTA-containing tube and centrifuged again at 3000 …