[Clinical and genetic analysis of a child with mosaic chromosome 8 trisomy syndrome]

To explore the genetic etiology of a child featuring recurrent oral ulcer.Clinical data of the child was collected. Whole exome sequencing was carried out for her. Candidate variant was verified by low-coverage massive parallel copy number variation sequencing (CNV-seq) of the family trio.The child, a 6-year-old girl, has featured recurrent fever and ulcers of the oral mucosa, vulvar and perianal regions. No pathogenic variant was found by whole exome sequencing. However, analysis of chromosome copy number variation using the whole exome sequencing data has revealed mosaicism of trisomy 8. CNV-seq assay has verified the variant in the child, with the percentage of mosaicism being 73%. No abnormality was found in neither of her parents.A case of mosaicism trisomy 8 with recurrent oral ulcer as the first symptom was diagnosed, which has enriched the phenotypic data of trisomy 8 syndrome.