Introduction
Reciprocal chromosomal translocation (RCT) is one of the most common human chromosomal abnormalities. Balanced RCT does not contain the variation in the number of chromosomes, but only the rearrangement of genetic material[1]. As we know, balanced RCT carriers will have greater risk to experience recurrent miscarriages, embryonic death, infertility or giving birth to defective offspring[2].
Copy number variants (CNVs) are also important causes of birth defects, resulting in various clinical manifestations, including growth and developmental abnormality, mental retardation, visceral malformation and special facial features, etc[3]. At present, various syndromes are verified to be caused by CNVs, such as 22q11.2 deletion syndrome, Cri-du-chat syndrome, Williams syndrome and so on[4].
Above all, birth defects are important challenges affecting the quality of the birth population. Genetic counseling as well as prenatal diagnosis is effective method to decrease the rate of birth defects[5].
In this study, we report the clinical findings detected in a Chinese pedigree [Figure 1]. The proband was diagnosed by CMA to carry a 25.6 Mb duplication of 8q24.12-q24.3 and a 16.5 Mb deletion of 18q21.33-q23. Karyotype analysis showed that the karyotype of the proband is paternally inherited 46,XX,der(18)t(8;18)(q24.1;q21.3). This is the first of such a kind of karyotype to be reported. At the same time, the mother of the proband was pregnant for 18 weeks. CMA and karyotype analysis of amniotic fluid cells indicated that the fetus also carried the same karyotype as that of the proband. The couple decided to terminate the pregnancy after genetic counseling. Functional enrichment analysis of the genes involved was also carried out to find out the key genes causing the phenotype of the proband.