Analysis of clinical characteristics and genetic variant in a child with Nicolaides-Baraitser syndrome due to maternal mosaicism

Objective: To carry out genetic testing for a child featuring global developmental delay, abnormal liver function, congenital heart disease, and brain malformation.

Methods: Peripheral blood samples of the child and his parents were collected for the extraction of genomic DNA and trio-whole exome sequencing. Candidate variant was verified by Sanger sequencing.

Results: Genetic testing revealed that the child has harbored a heterozygous c.2002G>T (p.Glu668Ter) variant of the SMARCA2 gene, which was predicted to be likely pathogenic by bioinformatic analysis. His mother was found to be a low-percentage mosaic for the same variant, with a ratio of 0.054 (246/4549).

Conclusions: The child was diagnosed with Nicolaides-Baraitser syndrome resulting from maternal mosaicism for the SMARCA2 gene variant.