Fetal de novo 6q24.3-q25.1 microdeletion encompassing TAB2 gene associated with small left atrium, growth restriction, and urogenital/anal abnormalities: a case report

Background Deletions involving TAB2 gene have been identified as the cause of a multi - system disorder, including cardiac abnormalities, distinctive facial features, growth abnormalities and connective tissue abnormalities. Cardiac abnormalities are a key feature and are present in nearly all patients. The majority of the reported patients are children or adults, while prenatal cases are rare. Whether cardiac abnormalities are the primary prenatal phenotype of TAB2 deficiency remains unclear. Case presentation: Here, we report a prenatal case where invasive prenatal diagnosis was performed because of thickened NT. The fetus had a normal karyotype. An SNP array analysis of the family revealed a de novo 1.12 Mb deletion on chromosome 6q24.3q25.1, which encompasses TAB2 gene. At 25 weeks of gestation, the fetus was found to have a small left atrium. Trio - based whole exome sequencing detected no pathogenic or likely pathogenic single nucleotide variants; however, it did identify the deletion on 6q24.3q25.1. Six weeks later, an ultrasound once more showed a small left atrium. Moreover, severe intrauterine growth restriction, hypospadias, and anal atresia were detected. The parents decided to terminate the pregnancy after genetic counseling. Subsequently, we reviewed all the TAB2 -related cases with available prenatal ultrasound findings. Conclusion The growth abnormalities resulting from 6q25.1 ( TAB2 ) microdeletion are more severe than cardiac abnormalities prenatally. We identified two new features, namely a small left atrium and anal atresia. Our study expands the spectrum of 6q25.1 ( TAB2 ) microdeletion and could provide evidence for the prenatal genetic counseling.