Your family medical history
Your family medical history helps in assessing your risk of developing a genetic disorder or passing one on to your children.
You may have noticed that some diseases seem to “run in your family”. These disorders may have a genetic basis or be due to lifestyle factors or a combination of the two. You can create a record of the disorders that have affected your family by making a medical family tree, which may help you to assess your own risk of disease.
Gathering family medical information
Information on your parents, brothers, and sisters is the most important, but you can provide a fuller picture by finding out about as many generations as possible, including your uncles, aunts, and grandparents.
It is also helpful to know something about your relatives' lifestyles to help you and your doctor to assess whether any diseases were largely due to behaviour or inheritance.
You may want to find out about your medical family tree out of curiosity, but you will find this information useful whenever a doctor needs to ask questions about illnesses in your family.
You are likely to be asked about your family medical history when you first see a new doctor; you are expecting a baby; if you are admitted to hospital; and if you develop symptoms of a disorder with a genetic component, such as asthma.
Assessing the information and drawing conclusions
You may be able to come to some conclusions about your risk of disease by looking at your medical family tree. If your investigation suggests that a particular disease has affected more than one member of your family, you should consult your doctor. In some cases, you may be referred for genetic counselling to assess your risk of developing a disorder or passing it on to your children.
Longevity runs in families, and, if many of your relatives lived beyond the age of 80, you have a good chance of doing the same, especially if you adopt a healthy lifestyle. If many of your relatives died young, you should try to find out the causes of death. You may be susceptible to disorders that have occurred more than once in your family.
You should suspect an inherited disorder if more than one child in your family was stillborn or died in childhood; if more than one adult died from heart disease or cancer before the age of 60; if more than two people in the family had a long-term disorder, such as arthritis; or if more than one family member had the same disabling or fatal disease.
Deaths before the age of 60 are especially relevant, unless they were caused by accidents or by an infection, such as tuberculosis, that occurred before effective treatment was available.
Professional interpretation of your family medical history
Genetic counsellors are trained to assess your risk of disease and determine whether you are a carrier of a faulty gene that causes a genetic disorder. Carriers do not have the disorder because the faulty gene is masked by a normal gene, but children of carriers can inherit the faulty gene. The counsellor will try to find out whether the high frequency of a disease in your family is due more to genetics or lifestyle.
For example, if colorectal cancer runs in your family, this could be due to eating habits shared by family members, since the disease may be associated with a high-fat, low-fibre diet. However, there may still be an inherited component.
Your family medical history may suggest that you are at risk of an inherited disorder. In this case, the counsellor will tell you whether a specific gene abnormality for the disorder has been identified and whether there is a diagnostic test to see if you have the gene (see Genetic tests). If a test is available, the counsellor can provide information that will help you to decide whether or not to have the test.
For example, you may be told whether the disease develops in everyone who inherits the faulty gene and whether preventive treatment is available. You may be told whether antenatal testing of the embryo or fetus is possible and what the implications are for any children you might have.
Some people decide not to proceed with genetic tests for a variety of reasons. Prospective parents may feel there is no point in worrying about a disorder that would not necessarily affect them or their child, or they may choose to carry on with a pregnancy even if there is an increased risk of their child being affected by a genetic disease.
They may also be concerned by the stigma associated with “labelling” someone as having or being a carrier of a disorder. Other people want to know the results of a test even if they would not act on them. Bear in mind that the test result for one family member may have implications for other family members who may not want to know the outcome.
Members of some ethnic groups are susceptible to particular genetic disorders, and individuals may be offered a screening test based on this fact alone. For example, 1 in 10 black people carries the gene for sickle-cell disease, a disorder of red blood cells. If you are Jewish, a genetic counsellor may recommend that you be screened for the metabolic disorder Tay-Sachs disease because 1 in 30 Ashkenazi Jews, compared with only 1 in 300 of the general population, carries the faulty gene that causes the disease.
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