Genetic disorders

A genetic disorder is a condition caused by abnormalities in a gene, which may involve a different form of a gene, called a variation or a mutation. Genetic mutations can occur as a result of exposure to environmental conditions or by chance but very little is known about why spontaneous mutations occur.

Many different health conditions and disorders have a genetic basis, such as cancer, which is caused by a single mutation in a gene or multiple mutations in a group of genes.

Some genetic disorders are inherited, which means the condition is passed on through a family and the risk of a child being born with an inherited condition is determined by their parent’s genetic information. If both parents are carriers of a disease, there is a high risk of their child being born with that disease.

In some cases, genetic disorders are caused by abnormalities with the chromosomes. A common example of a chromosomal disorder is Down’s syndrome, which is caused by an additional copy of chromosome 21.

Examples of genetic disorders

Chromosomal disorders: examples of chromosomal disorders include Down’s syndrome and fragile X syndrome.

Single gene disorders: these are disorders that are caused by abnormalities with a single gene; examples include cystic fibrosis, Huntington’s disease, sickle cell disease and muscular dystrophy.

Birth defects: many birth defects have a genetic basis; examples include neural tube defects and cleft lip and palate.

Familial cancer: some people have genes which mean that they have a high risk of developing a certain form of cancer, which is why numerous people in the same family may develop a specific form of cancer, for example a mother and her daughters may develop breast cancer.

Testing for genetic disorders

Genetic testing can be carried out for a number of reasons, including:

• if a patient has family history of condition and wants to know if they have a high risk of developing the condition
• if parents want to find out if they are carriers of a disease and there is a risk of passing on the condition to their child
• if a person is worried about family history of cancer
• if a person has medical problems or learning difficulties and doctors suspect that these problems may be associated with a genetic condition

Test results may be given alongside genetic counselling, as the results may not be good news. Genetic counselling is offered by specialists in medical genetics and is available on the NHS.