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Rare disease genomics

Get a better understanding of how whole genome sequencing can deliver better patient care for those with rare diseases.

Illustration of herd of zebras with one rainbow zebra in the middle of them
Finding answers

What we know about rare diseases

A rare disease is defined as one that affects less than 1 in 2,000 of the general population. There are between 5,000 and 8,000 known rare diseases.

In the UK, a single rare disease may affect up to about 30,000 people, though the vast majority of rare diseases will affect far fewer than this. Rare diseases include rare cancers such as childhood cancers, and some other well-known conditions such as cystic fibrosis and Huntington’s disease.


of rare diseases have a genomic component


of new cases found in children


of people are affected by a rare disease in their lifetime


people in the UK affected by a rare disease

Why do changes to DNA cause rare disease?

In about 80% of rare diseases, changes to DNA are involved in the cause.

DNA contains the instructions for making the proteins our bodies are built of – from the keratin in hair and fingernails to the antibody proteins that fight infection.

A change to DNA means a change to proteins. For example, this could be how the protein is built, or the amount of it that is made. Sometimes a change means that a protein doesn’t work properly. It could work too slowly, too quickly or not in the right way. If the protein is found in lots of areas of the body, then it could cause lots of different problems.

Improving prognosis for rare diseases using whole genome sequencing

Doctors will know that the disease is genetic, based on family history or symptoms. They will have clues about the cause. A patient may have had several genetic tests already. In these standard genetic tests, changes in specific genes are looked for.

Because only specific changes are looked for, if they are not there, the cause remains a mystery.

With whole genome sequencing, we look at every letter of DNA in a person’s genome. This gives us more chance of finding the change that is responsible for causing a disease.

Support for rare disease patients

Each of these charities or support organisations can provide information, support or services for families affected by rare diseases.

  • Contact A Family is a national charity for families with disabled children.

  • EURODIS, Rare Diseases Europe, is a patient-driven alliance of patient organisations representing 695 rare disease patient organisations in 63 countries.

  • Rare Disease UK is the national alliance for people with rare diseases and all who support them.

  • Genetic Alliance UK is the national charity working to improve the lives of patients and families affected by all types of genetic conditions.

  • SWAN, Syndromes Without A Name UK offers support and information to parents of children with undiagnosed genetic conditions.

  • Unique, Understanding chromosome disorders aim to inform, support and alleviate the isolation of anyone affected by a rare chromosome disorder and to raise public awareness.

  • For support with a specific rare disease, you can search for patient organisations and charities on the Rare Disease UK website.

For clinicians

Are you part of the healthcare workforce?

Learn more with Medics 4 Rare Diseases' Rare Disease 101 course, an online training for medical professionals.

M4RD provides education and practical tools targeted at medical professionals, enabling them to reduce the diagnostic odyssey and improve the patient experience.

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