Exome sequencing identified a de novo frameshift pathogenic variant of CTBP1 in an extremely rare case of HADDTS

Abstract

Hypotonia, ataxia, developmental delay, and tooth enamel defect syndrome (HADDTS) is an extremely rare autosomal dominant genetic disease caused by disruptive pathogenic variants in CTBP1. There are merely 12 cases reported to have pathogenic variants in the CTBP1 gene. Here, we report the first case with HADDTS in the Middle-Eastern population. In the present study, wholeexome sequencing was deployed to identify the variant(s) causing this condition. Subsequently, Sanger sequencing was performed to confirm the variant. The clinical evaluation of the patient is written according to the thoroughly carried out examinations and clinical investigations. A novel single frameshift pathogenic variant in CTBP1 (NM_001328.3:c.1315_1316delCA, p.Gln439ValfsTer84) was identified as the cause for HADDTS in the proband. Our findings enhance the knowledge of poorly studied CTBP1. The newly reported patient is phenotypically different in comparison to the previously reported cases. He has no sign of hypotonia, difficulty in walking or standing.