Objective: To explore the genetic basis of three children with unexplained developmental delay/intellectual disability (DD/ID).
Methods: Peripheral blood samples were collected from the patients and subjected to chromosomal microarray analysis (CMA).
Results: Patient 1 was found to harbor a 190 kb deletion at 9q34.3, which encompassed most of EHMT1 (OMIM 607001), the key gene for Kleefstra syndrome (OMIM 610253). Patients 2 and 3 were siblings. CMA showed that they have shared four chromosomal copy number variations (CNVs) including a deletion at 9q34.3 which spanned 154 kb and 149 kb, respectively, and encompassed the EHMT1 and CACNA1B (OMIM 601012) genes. The remaining 3 CNVs were predicted to be with no clinical significance.
Conclusion: Microdeletions at 9q33.4 probably underlay the pathogenesis of DD/ID in the three children, for which EHMT1 may be the key gene.