Prenatal diagnosis and molecular cytogenetic analyses of a rare 15q21.3 and 16p11.2 microduplication family.

Background: Copy number variants (CNVs) are an important source of normal and pathogenic genome variations. Microduplication of 15q21.3 is rare and is associated with an increased risk of developmental retardation, corpus callosum hypoplasia, microcephaly, cardiomyopathy, optic nerve hypoplasia and so on. Microduplication of 16p11.2 is associated with 16p11.2 microduplication syndrome (OMIM: 614671). The main clinical manifestations are low birth weight, microcephaly, mental retardation, language retardation, abnormal behavior, attention deficit, schizophrenia, affective disorder, loneliness spectrum disorder and so on. Individuals who carry these two microduplications are even more rare.

Materials and methods: In this research, a 32-year-old woman (gravida 1, para 0) underwent amniocentesis at 20 weeks' gestation because the results of ultrasound showed that one of the twins was smaller than the other.

Results: Copy number variation sequencing (CNV-seq) from this family revealed two types of microduplication (420 kb microduplication on chromosome 15q21.3 and 560 kb microduplication on chromosome 16p11.2) in both fetuses. Trio whole-exome sequencing (WES) showed that the two types of microduplication both originated from the father. After genetic counselling and being informed of the unfavourable prognosis, the parents decided to continue the pregnancy.

Conclusion: We provide a detailed description of the phenotype in a rare family with 15q21.3 and 16p11.2 microduplication. Combination of karyotype analysis, CNV-seq, WES, prenatal ultrasound and genetic counselling is helpful for the prenatal diagnosis of chromosomal microdeletions/microduplications.

Clinical trial number: Not applicable.