ABSTRACT
<p><b>OBJECTIVE</b>To investigate the association between genotype and phenotype of microdeletion and microduplication syndromes (MMSs) and the pathogenesis of pathogenic copy number variations (CNVs).</p><p><b>METHODS</b>A total of 50 children with MMSs diagnosed by chromosomal microarray analysis (CMA) from June 2013 to September 2015 were enrolled, and the clinical manifestations and features of pathogenic CNVs were analyzed.</p><p><b>RESULTS</b>The main clinical manifestations of children with MMSs included mental retardation, developmental delay, short stature, and unusual facies, with the presence of abnormalities in multiple systems. There were 54 pathogenic CNVs in total, consisting of 36 microdeletion segments and 18 microduplication segments, with sizes ranging from 28 kb to 48.5 Mb (mean 13.86 Mb). Pathogenic CNVs often occurred in chromosomes X, 15, and 1.</p><p><b>CONCLUSIONS</b>The clinical manifestations of MMSs are not specific, and a genotype-first approach can be used for diagnosis. Mode of inheritance, type of recombination (deletion or duplication), size of segment, and functional genes included helps with the interpretation of CNVs of de novo mutations, and in-depth research on rare pathogenesis may become breakthrough points for the identification of new MMSs.</p>