Prenatal diagnosis of trisomy 6q25.3-qter and monosomy 10q26.12-qter by array CGH in a fetus with an apparently normal karyotype

Reproductive outcomes in individuals with chromosomal reciprocal translocations

PURPOSE

Patients with reciprocal balanced translocations (RBT) have a risk for recurrent pregnancy losses (RPL), affected child, and infertility. Currently, genetic counseling is based on karyotypes found among the products of conception (POC), although factors influencing the success of assisted reproductive technologies (ART) in RBT couples are not established.

METHODS

Cytogenetic results from 261 POC and offspring of the parents (113 women and 90 men) with RBT were evaluated. Chromosome segregation modes and number of euploid embryos were assessed in couples undergoing in vitro fertilization.

RESULTS

Patients with translocations involving an acrocentric chromosome have a higher risk of unbalanced gametes caused by a 3:1 segregation. Female RBT patients have a statistically higher risk of aneuploidy due to an interchromosomal effect. The rate of euploid embryos is low due to meiosis I malsegregation of RBT, meiosis II nondisjunction, additional whole chromosome or segmental aneusomies. RBT patients with RPL have a higher rate of miscarriage of euploid fetuses with RBT.

CONCLUSION

Chromosome-specific factors, female gender, age, and history of RPL are the risk elements influencing pregnancy and in vitro fertilization success in RBT patients. Chromosomal microarray analysis of POC is necessary to provide an accurate and timely diagnosis for patients with adverse reproductive outcomes.

Prenatal diagnosis and ultrasonographic findings of partial trisomy of chromosome 6q: A case report and review of the literature

RATIONALE

Partial trisomy of the long arm of chromosome 6 syndrome is a rare chromosomal disorder with distinctive phenotypic expressivity, in which cytogenetic abnormalities are usually reported in infancy and childhood. Ultrasonographic findings on trisomy of the distal long arm of chromosome 6 in previous studies are limited.

PATIENT CONCERNS

A 32-year-old, gravida 6, para 1, pregnant woman who had 4 spontaneous abortions underwent a clinical ultrasound examination at 26 weeks of gestation.

DIAGNOSES

Ultrasonographic findings were microcephaly, an acoustic image of a transparent septum, a flat nasal bridge, right pulmonary artery stenosis, and a single umbilical artery. Cytogenetic and single-nucleotide polymorphism array analyses were performed to estimate genetic factors of this diagnosis by amniocentesis.

INTERVENTIONS

After genetic counseling, the patient and her husband opted to terminate the pregnancy.

OUTCOMES

Cytogenetic examination of the fetus showed the karyotype 46,XX,der(20)t(6;20)(q24;p13). The single-nucleotide polymorphism (SNP) array showed a 22.104-Mb duplication of 6q24.3q27 and a 0.784-Mb deletion of 20p13.

LESSONS

Ultrasonographic findings of fetal abnormalities, including microcephaly, an acoustic image of a transparent septum, a flat nasal bridge, right pulmonary artery stenosis, and a single umbilical artery, may be related to a 22.104-Mb duplication of 6q24.3q27 and a 0.784-Mb deletion of 20p13. More ultrasonographic and genotype studies are required to extend the phenotypic characterization of partial trisomy 6q syndrome.