Small 7p22.3 microdeletion: Case report of Snx8 haploinsufficiency and neurological findings

Abstract

Some cases of chromosome 7p22.3 deletions have been reported, but the genotype-phenotype correlation is still uncertain. Neurodevelopmental delay and heart anomalies have been recorded as the most recurrent defects. We describe the clinical features of a four-year-old male child with a 139 kb deletion at 7p22.3 involving SNX8 gene, inherited from a mosaic mother. The same deletion is also present in the fetus on the ongoing third pregnancy of the couple with normal fetal ultrasound assessment. The proband was prenatally diagnosed with left kidney agenesis. He does not show any congenital heart disease, but mild intellectual disability, learning and language delay, and severe behavioral problems related to the hyperactive-impulsive and inattentive area. These clinical features are also evident in other 7p22 deletions cases involving the SNX8 gene, supporting the role of this gene in neurodevelopment. Conversely, the revision of all published cases with small 7p22 deletions and the absence of heart malformations in the present family confirm that this region is involved in heart development, anyway did not confirm the role of SNX8 in cardiac phenotypes, either due to the reduced penetrance or the involvement of other candidate genes.

Keywords: 7p22.3 deletion; Mosaic deletion; SNX8; Tetralogy of fallot.