Genetic analysis of a child with Pitt-Hopkins syndrome due to a 18q21.2q21.32 deletion

Abstract

To explore the genetic etiology of a child featuring global developmental and mental retardation. Chromosome G-banding karyotype analysis, copy number variation sequencing (CNV-seq) and high-resolution chromosome banding were used to screen the genomic variant in the child and his parents. Both the child and his father were found to have a karyotype of 46,XY,del(18)(q21.1q21.3), whilst his mother was 46,XX. CNV-seq analysis showed that the child was arr[19]18q21.2-q21.32(chr18:48 422 190-58 039 582)×1, with a 10.58 Mb deletion which encompassed the TCF4 gene. The same deletion was found in neither parent. High-resolution banding revealed that the father has a fragment of 18q21.1q21.3 inserted into 5p13.1. The child was diagnosed with Pitt-Hopkins syndrome due to the 18q21.2q21.32 deletion. Chromosome karyotyping and CNV-seq can effectively identify submicroscopic chromosome anomalies.