Benign and pathogenic copy number variation on the short arm of chromosome 4.

The terminal deletion of the short arm of chromosome 4 causing the Wolf-Hirschhorn syndrome is one of the first pathogenic copy number variations (CNVs) ever described. Since this first discovery, a large number of 4p CNVs causing variable phenotypes have been described. Here, we present an overview on those benign and pathogenic visible and submicroscopic 4p imbalances. Interestingly, some CNVs can be, dependent on their copy number state, both benign and pathogenic. In addition, we show how the collection of both phenotypes and genotypes of 4p terminal deletions is leading towards the genetic dissection of the Wolf-Hirschhorn syndrome.