Chromosomal deletion
The deletion at 138275 is located at the long arm of chromosome 15, specifically at q11.2, within the region from 22,770,421 to 23,282,798, which corresponds to OMIM (615656).
What potential impacts could this have? The blood test has confirmed it is hereditary, but the mother is still very concerned.
Are there any similar studies or literature available?
Miss Lin, 30~39 year old female. Ask Date: 2018/08/26
Dr. Chen Ming reply Rare Disease
Please scan your report and send it to [email protected].
Additionally, call 04-7238595 ext.
7244 to request assistance from a genetic counselor to add me to the Chang Gung Memorial Hospital outpatient clinic.
God bless you.
[The case results do not specify the genome version, so the following explanation is based on the currently most commonly used hg19 version.]
Explanation:
1.
The deletion encompasses the 15q11.2 BP1-BP2 region, which can also be found in some healthy individuals.
However, recent studies have shown that 15q11.2 BP1-BP2 duplications/deletions are associated with developmental and behavioral abnormalities (von der Lippe et al., 2011; Burnside et al., 2011; Cox and Butler, 2015).
2.
This chromosomal variation can be a primary mutation or a familial inherited variation, with clinical symptoms exhibiting incomplete penetrance.
It is currently considered a risk locus.
3.
According to the analysis by Rosenfeld et al.
(2013), the estimated penetrance for the 15q11.2 BP1-BP2 deletion regarding overall abnormal external phenotypes after birth is approximately 10.4%.
4.
However, based on the analysis by Cooper et al.
(2011), the estimated penetrance for the 15q11.2 BP1-BP2 deletion concerning developmental delay is approximately 83%.
1.
von der Lippe C, et al.
15q11.2 microdeletion—seven new patients with delayed development and/or behavioral problems.
European Journal of Medical Genetics 2011;54:357-360.
2.
Burnside RD, et al.
Microdeletion/microduplication of proximal 15q11.2 between BP1 and BP2: a susceptibility region for neurological dysfunction including developmental and language delay.
Human Genetics 2011;130:517–528.
3.
Rosenfeld JA, et al.
Estimates of penetrance for recurrent pathogenic copy-number variations.
Genet Med.
2013;15(6):478-481.
4.
Cooper GM, et al.
A copy number variation morbidity map of developmental delay.
Nat Genet.
2011;43(9):838-846.
5.
Cox DM, Butler MG.
The 15q11.2 BP1-BP2 microdeletion syndrome: a review.
Int J Mol Sci.
2015;16(2):4068-4082.
Reply Date: 2018/08/26
More Info
Chromosome 15q11.2 microdeletions are associated with a variety of rare genetic disorders, and understanding their impact is crucial for affected individuals and their families. The specific region you mentioned, located between positions 22,770,421 and 23,282,798 on chromosome 15, is known to harbor genes that can influence neurodevelopmental and psychiatric conditions.
Microdeletions in this region can lead to a spectrum of clinical manifestations, including developmental delays, intellectual disabilities, autism spectrum disorders, and other neurobehavioral issues. The exact phenotype can vary significantly among individuals, even among those with the same deletion, due to factors such as genetic background and environmental influences.
The 15q11.2 region contains several important genes, including those involved in neuronal function and synaptic transmission. Disruptions in these genes can affect brain development and function, leading to the aforementioned conditions. For instance, the UBE3A gene, which is crucial for synaptic plasticity, is located in this region. While UBE3A is more commonly associated with Angelman syndrome when deleted, its involvement in other neurodevelopmental disorders is also being studied.
Regarding your concern about the hereditary nature of this microdeletion, it is essential to understand that microdeletions can be inherited from a parent or can occur de novo (new mutations not present in the parents). Genetic counseling can provide valuable insights into the inheritance patterns and the likelihood of recurrence in future pregnancies. If the deletion is confirmed to be inherited, it may be beneficial for family members to undergo genetic testing to assess their risk.
As for literature, there are several studies and reviews available that discuss the implications of 15q11.2 microdeletions. One notable resource is the Online Mendelian Inheritance in Man (OMIM) database, which provides detailed information about genetic conditions, including those associated with chromosome 15q11.2. Additionally, peer-reviewed journals such as "American Journal of Human Genetics" and "Journal of Medical Genetics" often publish articles on the clinical implications of chromosomal abnormalities.
It is understandable to feel anxious about the implications of a genetic diagnosis, especially when it concerns a child. Engaging with a genetic counselor or a specialist in genetics can help address your concerns, provide support, and guide you through the available resources and options for managing the condition. They can also assist in interpreting the genetic findings in the context of your family's health history and provide recommendations for monitoring and intervention if necessary.
In summary, chromosome 15q11.2 microdeletions can have significant implications for neurodevelopment and behavior. While the exact impact can vary, understanding the genetic basis and seeking appropriate support can help families navigate the challenges associated with these rare genetic conditions.
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