A comprehensive list of human microdeletion and microduplication syndromes

The phenotypic spectrum of human microdeletion and microduplication syndromes (MMS) is heterogeneous but often involves intellectual disability, autism spectrum disorders, dysmorphic features and/or multiple congenital anomalies. While the common recurrent copy number variants (CNVs) which underlie these MMS have been well-studied, the expansion of clinical genomic testing has led to the identification of many rare non-recurrent MMS. To date, hundreds of unique MMS have been reported in the medical literature, and no single resource exists which compiles all these MMS in one location.

Deletions and microdeletions

Loss of genetic material from the genome is known as a deletion or, if the deletion is too small to be seen under a microscope, a microdeletion.

Microdeletion and Microduplication Syndromes

Microdeletion syndromes differ from chromosomal deletion syndromes in that chromosomal deletion syndromes are usually visible on karyotyping because of their larger size (typically > 5 megabases), whereas the abnormalities in microdeletion syndromes involve smaller segments (typically 1 to 3 megabases) and are detectable only with fluorescent probes (fluorescent in situ hybridization) and chromosomal microarray analysis.

New microdeletion and microduplication syndromes: A comprehensive review

Several new microdeletion and microduplication syndromes are emerging as disorders that have been proven to cause multisystem pathologies frequently associated with intellectual disability (ID), multiple congenital anomalies (MCA), autistic spectrum disorders (ASD) and other phenotypic findings.

The discovery of microdeletion syndromes in the post-genomic era: review of the methodology and characterization of a new 1q41q42 microdeletion syndrome

Compared with the “phenotype-first” approach of traditional cytogenetics, array-based comparative genomic hybridization has enabled the detection of novel genomic disorders using a “genotype-first” approach.

What are microdeletion/microduplication syndromes?

Microdeletions and duplications are genetic abnormalities that involve the loss or duplication of a small segment of DNA from a chromosome. Unlike bigger genetic abnormalities like Down syndrome, which involve having an extra copy of an entire chromosome, microdeletions and duplications affect only a tiny portion of genetic material. These segments can range in size from a few hundred base pairs to several million.