Prenatal diagnosis and genetic counselling of a rare de-novo 12p13.33p13.32 deletion and 15q26.2q26.3 duplication in a Chinese family.

BACKGROUND: Copy number variants are an important source of normal and pathogenic genome variations. Constitutional deletions involving the distal part of the short arm of chromosome 12(12p13.33p13.32) are very rare. These deletions are associated with an emerging condition associated with variable phenotype, including a specific speech delay sound disorder, labeled childhood apraxia of speech, intellectual disability, and neurobehavioral problems. Trisomy of distal chromosome 15q has rarely been reported. It is generally believed that the terminal duplication of 15q26.2q26.3 is related to overgrowth phenotype, distinct facial features and intellectual disability.

MATERIALS AND METHODS: A 21-year-old woman (gravida 1, para 0) underwent amniocentesis at 26 weeks' gestation following the detection of a persistent left superior vena cava of the fetus on prenatal ultrasound. In this research, GTG-banding karyotype analysis, chromosomal microarray analysis (CMA), whole-exome sequencing (WES), and fluorescence in-situ hybridization (FISH) were performed.

RESULTS: CMA detected a 4.36 Mb deletion on chromosome 12p13.33p13.32 and a 7.59 Mb duplication on chromosome 15q26.2q26.3 of the fetus. No abnormality was found in the parents' genetic examination. After genetic counselling, the parents decided to continue the pregnancy.

CONCLUSION: We provide a detailed description of the prenatal diagnosis and genetic counselling of a rare de-novo 12p13.33p13.32 deletion and 15q26.2q26.3 duplication in a Chinese family. A combination of karyotype analysis, CMA, WES, FISH, prenatal ultrasound, and genetic counselling is helpful for the prenatal diagnosis of chromosomal deletions/duplications and pathogenic gene variants.