15q13.3 microdeletion syndrome - Unique - The Rare Chromosome ...

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arr[hg19]15q13.2q13.3 (30,971,330-32,439,084)x1 arr The analysis was by array (arr) comparative genomic hybridisation (cgh) hg19 Human Genome build 19. This is the reference DNA sequence that the base pair numbers refer to. As more information about the human genome is found, new “builds” of the genome are made and the base pair numbers may be adjusted 15q13.2q13.3 The chromosome involved is 15. The chromosome has two breakpoints, one in band 15q13.2 and one in band 15q13.3, and material between these two breakpoints is missing 30,971,330-32,439,084 The base pairs between 30,971,330 (around 31Mb) and 32,439,084 (around 32Mb) have been shown to be deleted. Take the first long number from the second and you get 1,467,754 (1.5Mb). This is the number of base pairs that are deleted x1 This means there is one copy of these base pairs, not two – one on each chromosome 15 – as you would normally expect Normal variant Some people have been found with a tiny amount of missing material slightly closer to the centromere, often where both breakpoints are within the 15q13.2 band but sometimes where both breakpoints are within the 15q13.3 band. Some of them are unaffected by this, others have some developmental difficulties. It is not yet known whether losing a very tiny amount of material from this region is a harmless variant or a variant which can disturb development in some people but not in others (Sharp 2008). 15q13.3 microdeletion syndrome The first published description of a person with a 15q13.3 microdeletion was in 2008. There have since been over 150 cases reported in the medical literature worldwide. When a particular set of developmental features occurs in a recognisable and consistent pattern in enough people with, as a result of a single cause, the condition is called a syndrome. The features of a 15q13.3 microdeletion do occur in this way, so the disorder is often known as 15q13.3 microdeletion syndrome. The deletion occurs equally often in males and females (Sharp 2008). How much do we know? Comparing different children and adults with 15q13.3 deletions shows that some effects seem to be very broadly similar. This information guide tells you what is known about those effects. Comparing your child’s array results with others, both in the medical literature and within Unique, can help to build up a general picture of what to expect. But there will still be differences, sometimes quite marked, between your child and others with an apparently similar array result. In families where more than one member has the 15q13.3 microdeletion, the specific effects can sometimes be quite different. It is very important to see your child as an individual and not to make direct comparisons with others with the same chromosome test results. After all, each of us is unique. 4
How common is it? It is surprisingly common— almost certainly found as often as much better known syndromes such as Prader-Willi, Angelman and Williams syndromes. It has been estimated that one person in every 30,000 to 40,000 in the general population has a 15q13.3 microdeletion although others have suggested that it might be even more common than that (Sharp 2008; van Bon 2009; LePichon 2010; Liao 2011). Most common features Every person with a 15q13.3 microdeletion is unique and so each person will have different medical and developmental concerns. Additionally, no one person will have all of the features listed in this information guide. However, a number of common features have emerged: • Generally no obvious birth defects • Children are likely to need support with learning. The amount of support needed by each child will vary • Seizures or abnormal results on EEG (electroencephalogram), but not in all children • Behavioural difficulties such as autistic spectrum disorder or attention deficit hyperactivity disorder. Some adults and children, but not all, have aggressive behaviour and rage • Subtly unusual facial features. Families may notice similarities between their own child and others with the deletion • Otherwise generally healthy Are there people with a 15q13.3 microdeletion who are healthy, have no major birth defects and have developed normally? There are many individuals with the microdeletion who appear normal and have no major birth defects, all of whom only discovered they had the deletion when it was detected in their children. Both fathers and mothers have passed a microdeletion on to their children (Sharp 2008; Ben-Shachar 2009; Pagnamenta 2009; van Bon 2009; Hoppman-Chaney 2012; Unique). If one person in a family with the 15q13.3 microdeletion is mildly affected, will others in the same family also be mildly affected? Not necessarily. There is a lot of variation between different members of the same family who have the same microdeletion. We know that if one person is mildly affected or unaffected, others may be more severely and obviously affected (Sharp 2008; Miller 2008; Ben-Shachar 2009; Pagnamenta 2009; van Bon 2009; Le Pichon 2010; Masurel-Paulet 2010; Liao 2011; Muhle 2011; Spielman 2011; Hoppman-Chaney 2012; Unique). What is the outlook? We can’t be certain yet but there appears to be no reason why people who are healthy should not enjoy a normal lifespan and there are a number of adults both at Unique and 5
Page 1 and 2: 15q13.3 microdeletion syndrome rare
Page 3: Looking at 15q13.3 You can’t see
Page 7 and 8: (floppiness) and weight loss. Two b
Page 9 and 10: Behaviour Some children with 15q13.
Page 11 and 12: “He has a lack of co-ordination a
Page 13 and 14: 2009; Pagnamenta 2009; van Bon 2009
Page 15 and 16: Puberty There is limited informatio
Page 17 and 18: Can it happen again? Where both par
Page 19 and 20: Notes 19

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