The following information may help to address your question:
Has a genetic link been established between trisomy 13, dextrocardia with sinus inversus, and Hirschsprung's disease?
An extensive search of available literature does not currently yield the presence of any genetic-based connection between any of these three disorders. They are not known to typically occur together in one individual or in families, nor are they known to be caused by similar abnormal genetic or developmental processes.
Last updated: 5/20/2015
What causes trisomy 13?
Most cases of trisomy 13 are caused by random events during the formation of eggs or sperm in healthy parents (prior to conception). Trisomy 13 is typically due to having three full copies of chromosome 13
in each cell in the body, instead of the usual two copies. This is referred to as complete trisomy 13 or full trisomy 13. The extra genetic material present disrupts the normal course of development, causing the characteristic features of the disorder.
Trisomy 13 can also occur when part of chromosome 13 becomes attached (translocated) to another chromosome during the formation of eggs or sperm, or very early in fetal development. This is referred to as translocation
trisomy 13. People with this type of trisomy 13 have the normal two normal copies of chromosome 13, plus an extra copy of chromosome 13 that is attached to another chromosome. Translocation trisomy 13 can be inherited. Approximately 20% of cases of trisomy 13 are caused by translocation trisomy 13.
In rare cases, only part of chromosome 13 is present in three copies in each cell (rather than the full chromosome); this is called partial trisomy 13. In other rare cases, a person has an extra copy of chromosome 13 in only some of the body's cells; this is called mosaic
trisomy 13. The severity of mosaic trisomy 13 depends on the type and proportion of cells that have the extra chromosome.
Last updated: 4/25/2016
Is trisomy 13 inherited?
Most cases of trisomy 13 are not inherited and result from random events during the formation of eggs and sperm in healthy parents. An error in cell division called nondisjunction results in an egg or sperm cell with an abnormal number of chromosomes. For example, an egg or sperm cell may gain an extra copy of chromosome 13. If one of these contributes to the genetic makeup of a child, the child will have an extra chromosome 13 in each cell of the body.
For a woman who has never had a pregnancy or child with a trisomy, the risk to have a pregnancy with a chromosome abnormality would typically be her age-related risk - the risk increases with maternal age. For a woman who has had an affected pregnancy or child in the past, the recurrence risk is generally quoted as about 1% or
the maternal age-related risk - whichever is higher at the time of pregnancy.
On the other hand, translocation trisomy 13 can be inherited. An unaffected parent can have a rearrangement of genetic material between chromosome 13 and another chromosome. These rearrangements are called balanced translocations because there is no extra or missing genetic material from chromosome 13. A person with a balanced translocation involving chromosome 13 has an increased chance of passing extra material from chromosome 13 to his/her children.
People interested in learning about their personal risk to have a child with a chromosome abnormality should speak with their health care provider or a genetics professional.
Last updated: 4/25/2016
What causes dextrocardia with situs inversus?
The exact cause of dextrocardia with situs inversus is not known, but the condition results from the abnormal positioning of the internal organs during fetal development. More than 60 known genes
are important for the proper positioning and patterning of the organs in the body. However, a specific genetic cause of dextrocardia with situs inversus has not been identified and inheritance patterns have not been confirmed in most cases.
Some people have dextrocardia with situs inversus as part of an underlying condition called primary ciliary dyskinesia
. Primary ciliary dyskinesia can result from changes (mutations
) in several different genes, including the DNAI1
gene; however, the genetic cause is unknown in many families.
Last updated: 5/19/2015
Is Hirschsprung's disease inherited?
Hirschsprung's disease (HSCR) usually occurs by itself without other symptoms and is called "isolated HSCR". Isolated HSCR has multifactorial inheritance
, which means that multiple genes interact with environmental factors to cause the condition. When someone has a child with isolated HSCR, the overall risk to have another child with the condition is 4%. There are some factors that can change the risk. For example, the risk is higher if the sibling has long-segment disease rather than short-segment disease. Also, males are more likely than females to develop HSCR. Another factor is if the siblings have the same or different parents.
for more information on genes associated with isolated HSCR
If HSCR occurs as part of a genetic syndrome
, then it is inherited in a specific pattern, according to the specific syndrome. For example, the inheritance may be autosomal recessive
, autosomal dominant
, or X-linked recessive
, depending on the exact cause of the syndrome.
In about 12% of the cases HSCR is part of a chromosome anomaly, such as Down syndrome
Individuals who are interested in learning about their personal risks or risks to family members should speak with their doctors or a genetics professional
Last updated: 10/17/2016
How can I find a genetics professional in my area?
Last updated: 7/15/2016
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