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Case Reports in Genetics
Volume 2013, Article ID 353028, 5 pages
http://dx.doi.org/10.1155/2013/353028
Case Report

An Interstitial 20q11.21 Microdeletion Causing Mild Intellectual Disability and Facial Dysmorphisms

1Mental Health Research Center, Russian Academy of Medical Sciences, Moscow 119152, Russia
2Institute of Pediatrics and Children Surgery, Ministry of Health of the Russian Federation, Moscow 125412, Russia
3Moscow City University of Psychology and Education, Moscow 127051, Russia

Received 30 November 2012; Accepted 9 January 2013

Academic Editors: S. Ennis, S. Paracchini, J. L. Royo, and M. Velinov

Copyright © 2013 Ivan Y. Iourov et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We report a case of an interstitial chromosome 20q11.21 microdeletion in a 7-year-old male child presenting with mild intellectual disability and facial dysmorphisms. Array comparative genomic hybridization (CGH) has shown that the deletion resulted in the loss of 68 genes, among which 5 genes (COX4I2, MYLK2, ASXL1, DNMT3B, and SNTA1) are disease causing. The size of the deletion was estimated to span 2.6 Mb. Only three cases of deletions encompassing this chromosomal region have been reported. The phenotype of the index patient was found to resemble the mildest cases of Bohring-Opitz syndrome that is caused by ASXL1 mutations. An in silico evaluation of the deleted genomic region has shown that benign genomic variations have never been observed to affect the ASXL1 gene, in contrast to the other disease-causing genes. As a result, it was suggested that ASXL1 loss is likely to be the main cause of the phenotypic manifestations. The present case report indicates that a loss of the disease-causing gene can produce a milder phenotype of a single gene condition.