Supernumerary chromosome inherited from a maternal balanced translocation leading to pure trisomy 9p

A Systematic Review of Reproductive Counseling in Cases of Parental Constitutional Reciprocal Translocation (9;22) Mimicking BCR-ABL1

We aim to determine the spectrum of cytogenetic abnormalities and outcomes in unbalanced offspring of asymptomatic constitutional balanced t(9;22) carriers through a systematic literature review. We also include a case of a constitutional balanced t(9;22) carrier from our institution. Among the 16 balanced t(9;22) carriers in our review, 13 were maternal and 3 were paternal. Of the 15 unbalanced translocation cases identified, 13 were live births, one was a missed abortion, and one resulted in pregnancy termination. The spectrum of established syndromes reported among the live births was the following: trisomy 9p syndrome (6/13), dual trisomy 9p and DiGeorge syndrome (3/13), dual 9q subtelomere deletion syndrome and DiGeorge syndrome (1/13), 9q subtelomere deletion syndrome (1/13), and DiGeorge syndrome (1/13). One unbalanced case did not have a reported syndrome. The phenotype of the unbalanced cases included cardiac abnormalities (5/13), neurological findings (7/13), intellectual disability (6/10), urogenital anomalies (3/13), respiratory or immune dysfunction (3/13), and facial or skeletal dysmorphias (13/13). Any constitutional balanced reciprocal t(9;22) carrier should be counseled regarding the increased risk of having a child with an unbalanced translocation, the spectrum of possible cytogenetic abnormalities, and predicted clinical phenotype for the unbalanced derivative.

Marker chromosomes

Marker chromosomes are a morphologically heterogeneous group of structurally abnormal chromosomes that pose a significant challenge in prenatal diagnosis. Phenotypes associated with marker chromosomes are highly variable and range from normal to severely abnormal. Clinical outcomes are very difficult to predict when marker chromosomes are detected prenatally. In this review, we outline the classification, etiology, cytogenetic characterization, and clinical consequences of marker chromosomes, as well as practical approaches to prenatal diagnosis and genetic counseling.