Proposal for Practical Approach in Prenatal Diagnosis of Beckwith–Wiedemann Syndrome and Review of the Literature

Maternal Cell-Free DNA Analysis in a Fetus Affected by Beckwith-Wiedemann Syndrome: Potential for Prenatal Diagnosis

Beckwith-Wiedemann syndrome (BWS) is a condition present from birth that involves excessive growth and is linked to changes in specific genes located on chromosome 11p15.5. Prenatal diagnosis is mainly based on imaging findings such as macrosomia, macroglossia, and omphalocele, but detection remains difficult. We report a case of a fetus suspected of having BWS based on prenatal ultrasound and MRI. A female infant was delivered via cesarean section at 37 weeks and one day of gestation, showing macrosomia, macroglossia, and other clinical features consistent with BWS. To explore potential biomarkers for prenatal diagnosis of BWS, maternal blood was collected at 36 and 37 weeks of gestation and postpartum days 1 and 5. Cell-free DNA (cfDNA) analysis revealed a bimodal fragment size distribution with peaks at 144 and 166 bp during pregnancy. After delivery, the 144 bp peak disappeared, resulting in a unimodal pattern. The fetal fraction was elevated during pregnancy (33.9-34.5%) and decreased rapidly postpartum (to 3.4%). These findings suggest an increased release of fetal-derived cfDNA with BWS-affected fetuses. This case highlights the potential utility of cfDNA analysis as a noninvasive biomarker for BWS.

Skewed X-Chromosome Inactivation and Parental Gonadal Mosaicism Are Implicated in X-Linked Recessive Female Hemophilia Patients

Background: Hemophilia A (HA) and B (HB) are X-linked recessive disorders that mainly affect males born from a mother carrier. Females are rarely affected but a number of mechanisms have been suggested in symptomatic females, such as skewed X-chromosome inactivation (XCI), chromosomal rearrangements, and hermaphrodites. Different methodologies are required to elucidate the underlying causes of such diseases in female patients. Methods: Three families with female hemophilia patients, including two HA and one HB, were enrolled for genetic analyses. Cytogenetics, molecular examinations on F8 and F9 genes, XCI assay, and linkage analysis were performed. Results: All three female patients are demonstrated to be heterozygous for an F8, or F9 mutation: one patient is inherited from her unaffected mother and the other two are sporadic cases. All three patients exhibit skewed XCI. The inherited patient is found to be unmethylated in the maternal X chromosome, which increases the potential for the expression of the mutant allele. The two sporadic cases are hypomethylated or unmethylated in the paternal X chromosome, suggesting that paternal gonadal mosaicism may exist in these families. Conclusions: In addition to screening for coagulation function, different genetic analyses are mandatory to explore the nature of mechanisms responsible for the X-linked recessive disorders in female patients as shown in this study. Our results confirm that skewed XCI is responsible for hemophilia in heterozygous female patients. Likewise, our results implicate that parental gonadal mosaicism, followed by skewed XCI, contributes to hemophilia in “sporadic” female patients.