Genetic Analysis of a Case of Sotos Syndrome with Suspected Germinal Mosaicism in Mother

This study is to identify the pathogenic mutation of a child with Sots syndrome and provide prenatal diagnosis for his pregnant mother. Chromosome microarray technology was used to detect whether there were minor deletions/duplication in patients' chromosomes. The gene mutation of patients was screened by next-generation sequencing technology, and it was verified by Sanger sequencing. Prenatal diagnosis of the fetus was conducted according to the selected pathogenic sites, and genetic counseling was conducted for her parents. Chromosome microarray results showed that there was no minor deletion in a chromosome 5q35 region, and the second-generation sequencing results showed that there was a c.4138delG heterozygous mutation in the patient's NSD1 gene, and the pathogenic of this mutation was not reported in related databases. Sanger sequencing found that there was a c.4138delG heterozygous mutation in the NSD1 gene of the patient and her parents' genotype at this locus was wild type. The prenatal gene test results indicated that there was heterozygous mutation of NSD1 gene c.4138delG in the fetus, so it was suggested to terminate the pregnancy. Gentling results indicated that the fetus and the patient inherited the same maternal chromosome 5. The heterozygous mutation of NSD1 gene c.4138delG is the pathogenic mutation of this Sots syndrome patient, and the mother may be germinal mosaicism.