Genetic analysis of a recurrent abnormal pregnancy case caused by a cryptic reciprocal autosomal translocation

Abstract

To provide genetic counseling for a couple with recurrent detection of fetal structural abnormality during second trimester pregnancy. The fetal tissue and peripheral blood samples of the couple were subjected to G banded chromosomal analysis, copy number variation sequencing (CNV-seq) and fluorescence in situ hybridization (FISH) assays. CNV-seq has detected a 6.59 Mb duplication at 7p22.3-p22.1 and a 3.81 Mb deletion at 4p16.3 in the fetal tissue, though conventional karyotyping results of both parents were normal. FISH has confirmed that the father has harbored a cryptic translocation of t(4;7)(7p+,4q+,4p+,7q+). The ultrasonographic abnormality of the fetuses may be attributed to the 7p microduplication and 4p microdeletion derived from the cryptic translocation carried by the father. Reciprocal translocation of tiny chromosomal segments should be suspected for couples with recurrent adverse pregnancies but apparently normal karyotypes.