The causality of de novo copy number variants is overestimated

The application of array CGH or chromosomal microarrays is causing a revolutionary change in clinical genetics and especially cytogenetics, as it enables the genome wide identification of submicroscopic copy number variations (CNVs).1 Given the significant increase in diagnostic yield compared with conventional karyotyping in patients with intellectual disability (ID) and the technical ease of use, the technique is now recommended as a first tier diagnostic test for patients with ID and/or multiple congenital anomalies (MCA).2, 3 Arrays not only enable detection of disease-causing CNVs in patients with ID/MCA, but also in patients with isolated heart defects, neurological diseases and psychiatric disorders. Therefore, besides pediatricians and clinical geneticists, more and more other medical specialists request array analysis arrays.4, 5, 6, 7 In addition, there is a rapid implementation of array CGH in prenatal diagnosis.8, 9, 10, 11