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The emerging microdeletion and microduplication syndromes: the importance of a diagnosis for both professionals and families
  1. J Hague,
  2. SL Wynn,
  3. P Middlemiss
  1. Unique, Rare Chrosome Disorder Support Group, Caterham, UK

Abstract

Background and aims Thousands of babies are born each year with errors in the make-up of their chromosomes which can affect their development, learning and behaviour although the effects are variable. These changes frequently constitute a chromosome imbalance: extra or missing chromosome material. Until recently these chromosome aberrations were detected by microscopic karyotype analysis and submicroscopic deletions and duplications were missed. Molecular techniques such as microarray-based comparative genomic hybridisation (arrayCGH) can today identify previously undetectable microdeletions and microduplications, some causing new syndromes. ArrayCGH offers families greater hope of a genetic diagnosis for their child despite the limitations of all genetic tests. The diagnosis of a new syndrome can alert both clinicians and families to future health problems and ensure appropriate screening is in place. Additionally, arrayCGH usually identifies the missing or duplicated genes, potentially improving counselling.

Methods Unique is a world-leading support group for families with a rare chromosome disorder (RCD). At November 2011, Unique has over 8,600 member families, representing more than 11,000 individuals. As diagnoses of RCDs increase, membership of Unique is also increasing.

Results ArrayCGH offers clinicians faced with a child with non-specific developmental delay, cognitive impairment or challenging behaviour a 20 percent diagnostic rate (compared to 7 percent with karyotype analysis).

This has led to a rise of over 100 percent in new members joining Unique annually in the period 2008 to 2010 (the period that arrayCGH was rolled out). For the 870 members joining Unique in November 2010-October 2011 arrayCGH was the most common genetic test used to diagnose their genetic disorder. Many are unique disorders, not previously reported in the medical literature.

In response to this, Unique has produced 19 new medically-verified guides on microdeletions and microduplications. Information guides are compiled from the medical literature; from Unique's database and other publicly available databases; and from detailed surveys completed by member families.

Conclusion The rapid increase in diagnosis of RCD made possible by arrayCGH has led to a steep rise in membership of Unique. We continue to publish new information guides in response to this, including newly-emerging microdeletion and microduplication syndromes.

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