Background: Congenital adrenal hyperplasia (CAH) arises from mutations in CYP21A2 gene, which encodes for the steroidogenic enzyme 21-hydroxylase. Currently employed chorionic villus sampling and amniocentesis provide genetic results at ~14 weeks of gestation at the earliest. At this time, the genitalia of the affected female foetuses have already become virilized. To prevent genital ambiguity, prenatal treatment with dexamethasone must begin on or before gestational week 9. This means that all mothers, even those pregnant with male and unaffected female foetuses, must receive dexamethasone before the genetic mutation are known, highlighting the need for earlier genetic diagnosis in utero.
Objective and hypotheses: Massively parallel sequencing (MPS) on plasma from pregnant mothers at 6 weeks of gestation could potentially provide the diagnosis of CAH, noninvasively, before the 9th week of gestation.
Method: Twenty families, each with a proband affected by classical CAH, were recruited. Cell free foetal DNA was obtained from 3.6 ml of maternal plasma. Using hybridization probes designed to capture a 6 Mb region flanking CYP21A2, targeted MPS was performed to analyze genomic DNA samples from parents and proband to determine parental haplotypes. Plasma DNA from pregnant mothers also underwent targeted MPS to deduce foetal inheritance of parental haplotypes.
Results: In twenty families, the foetal CAH status was correctly deduced by targeted MPS of DNA in maternal plasma, obtained as early as 5 weeks and 6 days of gestation.
Conclusion: MPS on 3.6 ml plasma obtained from pregnant mothers at 6 weeks of gestation could potentially provide the diagnosis of CAH, noninvasively, before the 9th week of gestation. Only affected female foetuses will thus be treated. Our strategy represents a generic approach for noninvasive prenatal testing for an array of autosomal recessive disorders.
01 - 03 Oct 2015
European Society for Paediatric Endocrinology