Rare diseases in three questions

On the occasion of the International Rare Disease Day, the Imagine Genetic Disease Center is organizing a series of events. For the occasion, the professor and director of the Stanislas Lyonnet Institute returns to the three major questions surrounding rare diseases.

What is a rare disease?

The definition of a rare disease is strictly numerical. This responds to a case count of less than 1 birth per 2,000 people. About three million French people are concerned. There are between 8,000 and 9,000 recognized rare diseases. Most rare diseases are expressed in the pediatric field. They are complex since they do not affect just one organ. Generally, there is also a hereditary component since 85% are genetic and half of them have identified mechanisms. Barely 10% of these patients benefit from a specific treatment thanks to a device that targets the alteration that leads to the disease.

How is a rare disease diagnosed?

At the birth of each child there is a systematic screening for several diseases. However, to diagnose a rare disease is very difficult. There is a path of the cross of diagnosis from the emergence of the first symptom until the moment when we put our finger on the disease. Too many families live in diagnostic wandering between the moment when we can name the symptoms and when we know the mechanisms of the disease. This difficulty can be explained in different ways. Some are inherent in the methodologies even if we are constantly progressing, there are still today failures in our health system to reduce this wandering as soon as possible. There are also scientific limits since, in the best conditions, diagnostic performance is, in some areas, capped at 50%. This is already progress since it was only 10% at the beginning of the 2000s.

What care for patients with a rare disease?

Three-quarters of rare diseases begin at pediatric age, so management usually begins in childhood. There is no more than 10% specific treatment, but we must be optimistic and tell ourselves that there is not just one therapeutic path, there are countless, like a kind of “Lépine competition for good ideas ”. Between gene epidemic research and the systematic screening of a molecule that could be active, there are dozens of replacement strategies. Medicine is firing on all cylinders, without dogmatism, to find ideas. At the Imagine centre, we bring together researchers, experts in rare diseases, doctors and patients so as not to miss a therapeutic path, while imposing a constant dialogue between all these entities. Then, to treat a rare disease, there is no rule. It’s a fight where all shots are allowed. Either a treatment has proven its effectiveness and it is then administered by a doctor in one of the rare disease centers, or a clinical trial is carried out with the patient. Moreover, these treatments, used for rare diseases, regularly lead to solutions that are then used for more common conditions.