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Phenotypic diversity of 15q11.2 copy number variants: a case series and review of the literature

Objectives: Breakpoint (BP)1 and BP2 of the proximal region of the long arm of chromosome 15 contains four highly-conserved and non-imprinted genes that function in neuronal connectivity and axonal growth: NIPA1, NIPA2, CYFIP1, TUBGCP5. In this case series, we report on phenotypic features of 17 patients with 15q11.2 copy number variants (CNVs) involving these genes. Furthermore, we compare them with other case series in the literature. Methods: This retrospective study is conducted on 17 patients with 15q11.2 CNVs. Brain magnetic resonance imaging, electroencephalography, chromosomal microarray results and the demographic/clinical data were obtained from the PROBEL hospital information management system. The Database of the Genomic Variants (DGV) and the Database of Chromosomal Imbalance and Phenotype in Humans using Ensembl Resources (DECIPHER) were checked for the interpretation of CNVs. Results: Of the 17 patients, 65%(n=11) had microduplication and 35%(n=6) had microdeletion in the 15q11.2 BP1-BP2 region. The mean size of the CNVs was 485±165 kb. Patients had a variety of phenotypic features including neurodevelopmental delay(59%), dysmorphic facial features(41%), epilepsy(41%), cognitive impairment(29%), behavioral problems/psychiatric symptoms(18%), hypotonicity(18%), scoliosis(12%), neuropathy with liability to pressure palsies(6%), microcephaly(6%), and hydrocephalus(6%). No significant difference was detected between the phenotypic features of microduplication and microdeletion groups of the study (all p>0.05). Conclusion: Copy number variants in the 15q11.2 BP1-BP2 region may not warrant a clinical outcome since the phenotypic variability and low penetrance. We believe that greater understanding of possible influences of the CNVs in this susceptibility locus will aid in our clinical approach in the future.
Keywords: 15q11.2, microdeletion, microduplication, copy number variant, phenotype.

Gunce Basarir
University of Health Sciences Izmir Tepecik Training and Research Hospital
Turkey

Irmak Erdogan
University of Health Sciences Izmir Tepecik Training and Research Hospital
Turkey

Nihal Olgac Dundar
Izmir Katip Celebi University, Faculty of Medicine, Department of Pediatric Neurology
Turkey

Berk Ozyilmaz
University of Health Sciences, Tepecik Training and Research Hospital
Turkey

Pinar Gencpinar
Izmir Katip Celebi University, Faculty of Medicine, Department of Pediatric Neurology
Turkey

 

 


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