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TRANSCRIPT
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Contact us If you live in the South East Thames Region: Clinical Genetics Department 7th Floor, Borough Wing, Guy’s Hospital, Great Maze Pond, London SE1 9RT t: 020 7188 1364, f: 020 7188 1369 w: www.guysandstthomas.nhs.uk/genetics
If both parents are healthy carriers of the same genetic condition, and if the gene change has been found, then prenatal testing may be possible by chorionic villus sampling (CVS) or amniocentesis testing. This option can be discussed at the genetics clinic, ideally before a pregnancy is conceived.
Which autosomal recessive disorders can be tested for? If a couple has a known family history of an autosomal recessive condition, it is best if they contact their GP or midwife, who can refer them to their local genetics centre to discuss their situation and the tests that may be available. Also, some autosomal recessive disorders are particularly common in some populations. A consanguineous couple could contact their GP or midwife, who can refer them to their local genetics centre to seek advice. The following screening is available for couples from the following ethnic backgrounds: sickle cell screening for couples from Africa
and the Caribbean thalassaemia screening for Asian, Middle
East and Mediterranean couples cystic fibrosis screening for white northern
European couples Tay Sachs disease for couples of Jewish
origin. How will the testing be done? For some couples at risk of passing on an autosomal recessive disorder, screening may be available.
This screening involves an initial blood test of both parents to determine whether or not they are carriers for a particular disorder. If the couple are both found to be carriers, a test can be offered in pregnancy to find out if the child is affected by the disorder. If the child is found to be affected, the parents can then decide if they wish to continue with the pregnancy or not.
Your comments and concerns For advice, support or to raise a concern, contact our Patient Advice and Liaison Service (PALS). To make a complaint, contact the complaints department. t: 020 7188 8801 (PALS) e: [email protected] t: 020 7188 3514 (complaints) e: [email protected] Pharmacy Medicines Helpline If you have any questions or concerns about your medicines, please speak to the staff caring for you or call our helpline. t: 020 7188 8748, Monday to Friday, 9am-5pm
Consanguinity This leaflet gives information about the risk of a child being affected by genetic condition if their parents are blood related (consanguineous).
Leaflet number: 2147/VER2 Date published: June 2019
Review date: June 2020 © 2019 Guy’s and St Thomas’ NHS Foundation Trust
A list of sources is available on request
2 3 4
What is consanguinity? Consanguinity comes from the Latin words ‘con’, meaning shared, and ‘sanguis’ meaning blood. Consanguinity refers to a situation in which a couple are blood relatives (they share an ancestor). An example is a couple who are first cousins. Consanguinity is common in many cultures and can have a number of social benefits. If a couple are consanguineous (related) their children have a higher chance of being affected by autosomal recessive genetic disorders. These only occur if a child has a mutation (change) in both copies of a particular gene pair.
Genes and autosomal recessive disorders Our bodies are made up of millions of cells. Inside each cell are 'instructions' telling our bodies how they should be made. These 'instructions' are divided into about 20,000 pairs of genes. Genes come in pairs with one copy inherited from our mother and one from our father. Sometimes a mutation can happen in a gene which can affect the ‘instruction’ produced by that gene. This could mean that a particular protein required for the body to work normally is missing or faulty, causing health problems. As our genes come in pairs we can have one changed copy as long as the other copy is normal and can compensate for the changed gene. A person with one changed copy of a gene pair is called a 'healthy carrier'.
For someone to be affected with an autosomal recessive disorder, they must have two changed copies of a particular gene. For example, someone with cystic fibrosis (a common autosomal recessive disorder in Europe) has two mutated copies of the cystic fibrosis gene.
What if a couple are both healthy carriers of the same condition? There is a chance they could have children affected by the condition. Each parent only passes on one copy of each of their genes. If both parents are healthy carriers of the same condition then with each pregnancy there are a number of possible outcomes: a 1 in 4 (25%) chance that the child could
be affected. a 1 in 2 (50%) chance that the child could
be a healthy carrier. a 1 in 4 (25%) chance that the child could
have two normal copies of the gene and so would not be a carrier or affected.
The parents of a child with an autosomal recessive condition are usually both healthy carriers of that condition.
Why are related couples more likely to have a child with an autosomal recessive disorder? Everyone is thought to be a healthy carrier of several changed genes. Unrelated couples usually have alterations in different genes. This means that an unrelated couple have a low risk of having a child with an autosomal recessive condition.
A related couple are more likely to have an alteration to the same gene because they have both inherited some of their genes from their shared relatives. In the case of first cousins, both of them could have inherited the same changed gene from one of the grandparents that they share. The more distantly related a couple is, the fewer gene copies they will share, so the risk that they will have a child with an autosomal recessive disorder is lower.
What is the chance of having a child with severe abnormalities? Unrelated parents have a risk of about 2 in 100 (2%) of having a child with an abnormality from birth, which can be severe/lethal. Parents who are first cousins have an extra risk of about 3 in 100 (3%), giving them a total risk of about 5 in 100 (5%). Parents who are first cousins once removed, or second cousins, have an additional risk of about 1 in 100 (1%) and a total risk of about 3 in 100 (3%). If there is no family history of a recessive disorder, most children of first cousins and more distant relatives will be healthy – over 95 in 100 (95%).
Can abnormalities be detected in pregnancy? Some abnormalities may be detected on a specialised ultrasound scan. Scanning detects about half of these severe abnormalities at around 20 weeks of pregnancy. These scans can be easily arranged by a midwife, genetics department or GP.
2 3 4
What is consanguinity? Consanguinity comes from the Latin words ‘con’, meaning shared, and ‘sanguis’ meaning blood. Consanguinity refers to a situation in which a couple are blood relatives (they share an ancestor). An example is a couple who are first cousins. Consanguinity is common in many cultures and can have a number of social benefits. If a couple are consanguineous (related) their children have a higher chance of being affected by autosomal recessive genetic disorders. These only occur if a child has a mutation (change) in both copies of a particular gene pair.
Genes and autosomal recessive disorders Our bodies are made up of millions of cells. Inside each cell are 'instructions' telling our bodies how they should be made. These 'instructions' are divided into about 20,000 pairs of genes. Genes come in pairs with one copy inherited from our mother and one from our father. Sometimes a mutation can happen in a gene which can affect the ‘instruction’ produced by that gene. This could mean that a particular protein required for the body to work normally is missing or faulty, causing health problems. As our genes come in pairs we can have one changed copy as long as the other copy is normal and can compensate for the changed gene. A person with one changed copy of a gene pair is called a 'healthy carrier'.
For someone to be affected with an autosomal recessive disorder, they must have two changed copies of a particular gene. For example, someone with cystic fibrosis (a common autosomal recessive disorder in Europe) has two mutated copies of the cystic fibrosis gene.
What if a couple are both healthy carriers of the same condition? There is a chance they could have children affected by the condition. Each parent only passes on one copy of each of their genes. If both parents are healthy carriers of the same condition then with each pregnancy there are a number of possible outcomes: a 1 in 4 (25%) chance that the child could
be affected. a 1 in 2 (50%) chance that the child could
be a healthy carrier. a 1 in 4 (25%) chance that the child could
have two normal copies of the gene and so would not be a carrier or affected.
The parents of a child with an autosomal recessive condition are usually both healthy carriers of that condition.
Why are related couples more likely to have a child with an autosomal recessive disorder? Everyone is thought to be a healthy carrier of several changed genes. Unrelated couples usually have alterations in different genes. This means that an unrelated couple have a low risk of having a child with an autosomal recessive condition.
A related couple are more likely to have an alteration to the same gene because they have both inherited some of their genes from their shared relatives. In the case of first cousins, both of them could have inherited the same changed gene from one of the grandparents that they share. The more distantly related a couple is, the fewer gene copies they will share, so the risk that they will have a child with an autosomal recessive disorder is lower.
What is the chance of having a child with severe abnormalities? Unrelated parents have a risk of about 2 in 100 (2%) of having a child with an abnormality from birth, which can be severe/lethal. Parents who are first cousins have an extra risk of about 3 in 100 (3%), giving them a total risk of about 5 in 100 (5%). Parents who are first cousins once removed, or second cousins, have an additional risk of about 1 in 100 (1%) and a total risk of about 3 in 100 (3%). If there is no family history of a recessive disorder, most children of first cousins and more distant relatives will be healthy – over 95 in 100 (95%).
Can abnormalities be detected in pregnancy? Some abnormalities may be detected on a specialised ultrasound scan. Scanning detects about half of these severe abnormalities at around 20 weeks of pregnancy. These scans can be easily arranged by a midwife, genetics department or GP.
2 3 4
What is consanguinity? Consanguinity comes from the Latin words ‘con’, meaning shared, and ‘sanguis’ meaning blood. Consanguinity refers to a situation in which a couple are blood relatives (they share an ancestor). An example is a couple who are first cousins. Consanguinity is common in many cultures and can have a number of social benefits. If a couple are consanguineous (related) their children have a higher chance of being affected by autosomal recessive genetic disorders. These only occur if a child has a mutation (change) in both copies of a particular gene pair.
Genes and autosomal recessive disorders Our bodies are made up of millions of cells. Inside each cell are 'instructions' telling our bodies how they should be made. These 'instructions' are divided into about 20,000 pairs of genes. Genes come in pairs with one copy inherited from our mother and one from our father. Sometimes a mutation can happen in a gene which can affect the ‘instruction’ produced by that gene. This could mean that a particular protein required for the body to work normally is missing or faulty, causing health problems. As our genes come in pairs we can have one changed copy as long as the other copy is normal and can compensate for the changed gene. A person with one changed copy of a gene pair is called a 'healthy carrier'.
For someone to be affected with an autosomal recessive disorder, they must have two changed copies of a particular gene. For example, someone with cystic fibrosis (a common autosomal recessive disorder in Europe) has two mutated copies of the cystic fibrosis gene.
What if a couple are both healthy carriers of the same condition? There is a chance they could have children affected by the condition. Each parent only passes on one copy of each of their genes. If both parents are healthy carriers of the same condition then with each pregnancy there are a number of possible outcomes: a 1 in 4 (25%) chance that the child could
be affected. a 1 in 2 (50%) chance that the child could
be a healthy carrier. a 1 in 4 (25%) chance that the child could
have two normal copies of the gene and so would not be a carrier or affected.
The parents of a child with an autosomal recessive condition are usually both healthy carriers of that condition.
Why are related couples more likely to have a child with an autosomal recessive disorder? Everyone is thought to be a healthy carrier of several changed genes. Unrelated couples usually have alterations in different genes. This means that an unrelated couple have a low risk of having a child with an autosomal recessive condition.
A related couple are more likely to have an alteration to the same gene because they have both inherited some of their genes from their shared relatives. In the case of first cousins, both of them could have inherited the same changed gene from one of the grandparents that they share. The more distantly related a couple is, the fewer gene copies they will share, so the risk that they will have a child with an autosomal recessive disorder is lower.
What is the chance of having a child with severe abnormalities? Unrelated parents have a risk of about 2 in 100 (2%) of having a child with an abnormality from birth, which can be severe/lethal. Parents who are first cousins have an extra risk of about 3 in 100 (3%), giving them a total risk of about 5 in 100 (5%). Parents who are first cousins once removed, or second cousins, have an additional risk of about 1 in 100 (1%) and a total risk of about 3 in 100 (3%). If there is no family history of a recessive disorder, most children of first cousins and more distant relatives will be healthy – over 95 in 100 (95%).
Can abnormalities be detected in pregnancy? Some abnormalities may be detected on a specialised ultrasound scan. Scanning detects about half of these severe abnormalities at around 20 weeks of pregnancy. These scans can be easily arranged by a midwife, genetics department or GP.
5
Contact us If you live in the South East Thames Region: Clinical Genetics Department 7th Floor, Borough Wing, Guy’s Hospital, Great Maze Pond, London SE1 9RT t: 020 7188 1364, f: 020 7188 1369 w: www.guysandstthomas.nhs.uk/genetics
If both parents are healthy carriers of the same genetic condition, and if the gene change has been found, then prenatal testing may be possible by chorionic villus sampling (CVS) or amniocentesis testing. This option can be discussed at the genetics clinic, ideally before a pregnancy is conceived.
Which autosomal recessive disorders can be tested for? If a couple has a known family history of an autosomal recessive condition, it is best if they contact their GP or midwife, who can refer them to their local genetics centre to discuss their situation and the tests that may be available. Also, some autosomal recessive disorders are particularly common in some populations. A consanguineous couple could contact their GP or midwife, who can refer them to their local genetics centre to seek advice. The following screening is available for couples from the following ethnic backgrounds: sickle cell screening for couples from Africa
and the Caribbean thalassaemia screening for Asian, Middle
East and Mediterranean couples cystic fibrosis screening for white northern
European couples Tay Sachs disease for couples of Jewish
origin. How will the testing be done? For some couples at risk of passing on an autosomal recessive disorder, screening may be available.
This screening involves an initial blood test of both parents to determine whether or not they are carriers for a particular disorder. If the couple are both found to be carriers, a test can be offered in pregnancy to find out if the child is affected by the disorder. If the child is found to be affected, the parents can then decide if they wish to continue with the pregnancy or not.
Your comments and concerns For advice, support or to raise a concern, contact our Patient Advice and Liaison Service (PALS). To make a complaint, contact the complaints department. t: 020 7188 8801 (PALS) e: [email protected] t: 020 7188 3514 (complaints) e: [email protected] Pharmacy Medicines Helpline If you have any questions or concerns about your medicines, please speak to the staff caring for you or call our helpline. t: 020 7188 8748, Monday to Friday, 9am-5pm
Consanguinity This leaflet gives information about the risk of a child being affected by genetic condition if their parents are blood related (consanguineous).
Leaflet number: 2147/VER2 Date published: June 2019
Review date: June 2020 © 2019 Guy’s and St Thomas’ NHS Foundation Trust
A list of sources is available on request
5
Contact us If you live in the South East Thames Region: Clinical Genetics Department 7th Floor, Borough Wing, Guy’s Hospital, Great Maze Pond, London SE1 9RT t: 020 7188 1364, f: 020 7188 1369 w: www.guysandstthomas.nhs.uk/genetics
If both parents are healthy carriers of the same genetic condition, and if the gene change has been found, then prenatal testing may be possible by chorionic villus sampling (CVS) or amniocentesis testing. This option can be discussed at the genetics clinic, ideally before a pregnancy is conceived.
Which autosomal recessive disorders can be tested for? If a couple has a known family history of an autosomal recessive condition, it is best if they contact their GP or midwife, who can refer them to their local genetics centre to discuss their situation and the tests that may be available. Also, some autosomal recessive disorders are particularly common in some populations. A consanguineous couple could contact their GP or midwife, who can refer them to their local genetics centre to seek advice. The following screening is available for couples from the following ethnic backgrounds: sickle cell screening for couples from Africa
and the Caribbean thalassaemia screening for Asian, Middle
East and Mediterranean couples cystic fibrosis screening for white northern
European couples Tay Sachs disease for couples of Jewish
origin. How will the testing be done? For some couples at risk of passing on an autosomal recessive disorder, screening may be available.
This screening involves an initial blood test of both parents to determine whether or not they are carriers for a particular disorder. If the couple are both found to be carriers, a test can be offered in pregnancy to find out if the child is affected by the disorder. If the child is found to be affected, the parents can then decide if they wish to continue with the pregnancy or not.
Your comments and concerns For advice, support or to raise a concern, contact our Patient Advice and Liaison Service (PALS). To make a complaint, contact the complaints department. t: 020 7188 8801 (PALS) e: [email protected] t: 020 7188 3514 (complaints) e: [email protected] Pharmacy Medicines Helpline If you have any questions or concerns about your medicines, please speak to the staff caring for you or call our helpline. t: 020 7188 8748, Monday to Friday, 9am-5pm
Consanguinity This leaflet gives information about the risk of a child being affected by genetic condition if their parents are blood related (consanguineous).
Leaflet number: 2147/VER2 Date published: June 2019
Review date: June 2020 © 2019 Guy’s and St Thomas’ NHS Foundation Trust
A list of sources is available on request