13q13.3 microdeletion associated with apparently balanced translocation of 46,XX,t(7;13) suggests NBEA involvement

Abstract

Background: Deletion of 13q13.3 is an extremely rare event.

Case: We report on a 25-month-old girl with neurodevelopmental disorder and intellectual disability. She had dysmorphic facies characterized by synophrys, long and narrow palpebral fissures; and a large, round face with small organs such as the eyes and mouth positioned near the center. She was hypotonic and had autism-like behaviors. Blood tests and brain MRI revealed no specific findings. However, G-banding chromosome analysis showed an apparently balanced translocation: 46,XX,t(7,13)(q11.23;q12.3). Both parents had normal karyotypes. Furthermore, her abnormal phenotype and chromosomal breakpoint lesion were suspected to be associated. Hence, we conducted array comparative genomic hybridization, which revealed a 3.2 Mb novel pathological microdeletion at 13q13.3 involving 17 genes including neurobeachin (NBEA), a neurodevelopment disorder gene. Furthermore, fluorescence in situ hybridization using probes adjacent to the microdeletion suggested a concomitant occurrence of the deletion and translocation as the structural basis of this rare genomic variant.

Conclusion: NBEA may have roles in her neurodevelopmental phenotypes, whereas other genes within the 13q13.3 microdeletion may contribute to her dysmorphic features.

Keywords: 13q13.3 microdeletion; Apparently balanced chromosomal translocation; Intellectual disability; Neurodevelopmental disorder; array-Comparative Genomic Hybridization (a-CGH).