Today is Rare Disease Day. Its main aim is to raise awareness among policy makers and the general public. There are over 6,000 rare diseases and 80% of these have a genetic cause.

We have over 20,000 genes coded by over 3,000,000,000 letters of genetic code. Genetic diseases are caused by mistakes in one or more of these genes. These are like typos or spelling mistakes. Not all genetic changes cause disease. But some debilitating genetic diseases are caused by simple one-letter mistakes.

There are also longer mistakes – sections of chromosome can be taken out (deleted) or added in. People with chromosomal syndromes are likely to have several unrelated symptoms, because a cluster of different genes is affected.

The more common genetic diseases are more likely to be researched. There were several labs working to discover the genes for some of the more well-known diseases at the same time – such as cystic fibrosis, Duchenne muscular dystrophy and fragile X syndrome. This competition created a sense of urgency that helped speed up the discovery of these genes. Finding out what gene causes a disease can go a long way to understanding the disease. Sometimes very effective treatments are found by knowing the cause of a disease. The more common genetic diseases that still aren’t fully explained are usually caused by the combined effect of multiple genes. It’s a lot harder to track these down. But there are probably still a lot of rare diseases that could be simply explained but aren’t being researched.

A lack of awareness of rare diseases often means there is misdiagnosis or difficulty getting a diagnosis. People with rare diseases have shared their stories on the Rare Disease Day websites. This is Judit’s story (Judit stars in this video).