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Locus heterogeneity in two siblings presenting with developmental delay, intellectual disability and autism spectrum disorder.
Gene 768:145260 (2021)
Correct diagnosis of children presenting with developmental delay and intellectual disability remains challenging due to the complex and heterogeneous etiology. High throughput sequencing technologies like exome sequencing have become more commonly available and are significantly improving genetic testing. We present two siblings – a 14-year old male and an 8-year old female patient – with a similar clinical phenotype that was characterized by combined developmental delay primarily affecting speech, mild to moderate intellectual disability, behavioral abnormalities, and autism spectrum disorder, but with no congenital anomalies. The sister showed additional muscular hypotonia and more pronounced dysmorphic features compared to her brother. Both parents had psychiatric disorders and mild to moderate intellectual disability. A common genetic etiology in the siblings was suspected. Metabolic, psychological and neuroradiological examinations were complemented by basic genetic testing including chromosome analysis and array comparative genomics hybridization analysis (CGH), followed by exome sequencing and combined data analysis of the family. Exome sequencing identified two different underlying genetic conditions: in the sister, a maternally inherited pathogenic variant c.1661C > T, p.Pro554Leu in SLC6A8 (NM_005629.4) was identified causing cerebral creatine deficiency syndrome 1 (MIM #300352) which was confirmed by MR spectroscopy and treated accordingly. In the brother, a paternally inherited 16p13.11 duplication was identified by exome sequencing and considered to be likely associated with his and possibly his father's phenotype. The 16p13.11 duplication had been previously identified in an array CGH but had not been prioritized due to the lack of segregation in the siblings. In conclusion, we report a case of intra-familial locus heterogeneity of developmental delay in two siblings. We advocate for the need of unbiased and comprehensive genetic testing to provide accurate diagnosis despite locus heterogeneity.
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Publication type
Article: Journal article
Document type
Scientific Article
Keywords
Creatine Transporter Deficiency ; Developmental Disorders ; Duplication 16p13.11 ; Intellectual Disability ; Locus Heterogeneity ; Slc6a8; Creatine Transporter Defect; Mental-retardation; Mutations; Variants; Males
ISSN (print) / ISBN
0378-1119
e-ISSN
1879-0038
Journal
Gene
Quellenangaben
Volume: 768,
Article Number: 145260
Publisher
Elsevier
Publishing Place
Radarweg 29, 1043 Nx Amsterdam, Netherlands
Non-patent literature
Publications
Reviewing status
Peer reviewed
Institute(s)
Institute of Neurogenomics (ING)