Noonan syndrome is a relatively rare genetic disorder, affecting around 1 in every 1,000 to 2,500 children born. Patients often have a tendency to bleed more easily, particularly from the skin or mucocutaneous tissue (such as mouth or nose). Around half of all the patients are affected by bleedings. The causes of bleeding are variable : some are linked to platelet disorders, others to more complex coagulation problems. However, it is difficult to predict exactly which patients are at risk of severe bleeding, for example during surgery. This is why there are as yet no clear recommendations for preventing this risk before medical intervention. However, it is recommended that patients with Noonan syndrome consult a specialist to assess this risk. Unfortunately, the tests carried out are often unreliable in predicting this significant risk of bleeding. In this study, data from a large group of patients with Noonan syndrome, followed-up in different centers in France, will be studied. During a medical meeting as part of their regular follow-up, a medical doctor assessed their tendency to bleed using a standardized questionnaire (standardized ISTH-BAT score). These results will be compared with the biological tests also performed during their medical follow-up. The aim is to better understand whether these tests are useful in predicting the risk of bleeding. Ultimately, this could help practicians to better anticipate surgical or medical interventions in these patients, and limit bleeding-related risk.