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Introduction: Aneuploids, copy number variations (CNVs), and single
nucleotide variants in specific genes are the main genetic causes of
developmental delay (DD) and intellectual disability disorder (IDD).
These genetic changes can be detected using chromosome analysis,
chromosomal microarray (CMA), and next-generation DNA sequencing
techniques. Therefore; In this study, we aimed to investigate the
importance of CMA in determining the genomic etiology of unexplained
DD and IDD in 123 patients.
Method: For 123 patients, chromosome analysis, DNA fragment analysis
and microarray were performed. Conventional G-band karyotype
analysis from peripheral blood was performed as part of the initial
screening tests. FMR1 gene CGG repeat number and methylation
analysis were carried out to exclude fragile X syndrome.
Results: CMA analysis was performed in 123 unexplained IDD/DD
patients with normal karyotypes and fragile X screening, which were
evaluated by conventional cytogenetics. Forty-four CNVs were detected
in 39 (39/123=31.7%) patients. Twelve CNV variant of unknown
significance (VUS) (9.75%) patients and 7 CNV benign (5.69%) patients
were reported. In 6 patients, one or more pathogenic CNVs were
determined. Therefore, the diagnostic efficiency of CMA was found to
be 31.7% (39/123).
Conclusion: Today, genetic analysis is still not part of the routine in the
evaluation of IDD patients who present to psychiatry clinics. A genetic
diagnosis from CMA can eliminate genetic question marks and thus
alter the clinical management of patients. Approximately one-third
of the positive CMA findings are clinically intervenable. However, the
emergence of CNVs as important risk factors for multiple disorders
increases the need for individuals with comorbid neurodevelopmental
conditions to be the priority where the CMA test is recommended.
Keywords: Copy number variations, chromosomal microarray,
developmental delay, intellectual developmental disorder, mental
retardation, genetic testing