Application of array comparative genomic hybridization in Korean children under six years old with global developmental delay

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Objective: Recent advancements in molecular techniques have greatly contributed to the discovery of genetic causes of unexplained developmental delay. Here, we describe the results of array comparative genomic hybridization (CGH) and the clinical features of 27 patients with global developmental delay. Methods: We included 27 children who met the following criteria: (1) Korean children under 6 years with global developmental delay; (2) had at least one or more physical or neurological problem other than global developmental delay; and (3) in whom both array CGH and G-banded karyotyping tests were performed. Results: Fifteen male patients and 12 female patients with a mean age of 29.3±17.6 months were included. The most common physical and neurological abnormalities were facial dysmorphism (n = 16), epilepsy (n = 7), and hypotonia (n = 7). Pathogenic copy number variation results were observed in 4 patients (14.8%): 18.73 Mb dup(2)(p24.2p25.3) and 1.62 Mb del(20p13) (patient 1); 22.31 Mb dup(2)(p22.3p25.1) and 4.01 Mb dup(2)(p21p22.1) (patient 2); 12.08 Mb del(4)(q22.1q24) (patient 3); and 1.19 Mb del(1)(q21.1) (patient 4). One patient (3.7%) displayed a variant of uncertain significance. Four patients (14.8%) displayed discordance between G-banded karyotyping and array CGH results. Among patients with normal array CGH results, four (16%) revealed brain anomalies such as schizencephaly and hydranencephaly. One patient was diagnosed with Rett syndrome and one with Möbius syndrome. Conclusion: As chromosomal microarray can elucidate the cause of previously unexplained developmental delay, it should be considered as a first-tier cytogenetic diagnostic test for children with unexplained developmental delay.