Abstract:

We report a case of theoretically inconsistent results between the prenatal diagnosis and previous chromosomal karyotype analysis at Affiliated Hospital of Guangdong Medical University (our hospital). The previous previous karyotype analysis of peripheral blood from an outside hospital suggested 46,XX,t(1;5)(p36;q22) in the pregnant woman, and 46,XY,inv(Y)(p11q11) in her spouse. However, the amniotic fluid karyotype at our hospital was 46,XN,ins(1;5)(p33;q34q21). According to the theory of gamete segregation of reciprocal translocation carriers, if the previous diagnosis is translocation, it is theoretically difficult to explain the current fetal karyotype, considering that the results of previous chromosomal karyotype analysis in the pregnant woman could be biased. For further verification, the pregnant woman was suggested to higher-level hospital for high-resolution G-banding review, and the peripheral blood karyotype of the pregnant women was confirmed to be 46,XX,ins(1;5)(p32.2;q33.2q22), which was consistent with the results of amniotic fluid karyotype from our hospital. This case suggests that the conventional G-banding has limited resolution for complex or atypical chromosomal structural abnormalities, especially when complex rearrangements are involved. It is necessary to further conduct high-resolution banding to accurately locate break points and rearrangement types, in combination with theoretical knowledge, so as to avoid affecting genetic counseling based on wrong diagnosis.

Key words: Prenatal diagnosis, Chromosome aberrations, Karyotyping, Translocation, genetic, Mutagenesis, insertional