Introduction: Williams-Beuren syndrome is a rare genetic disorder caused by a 7q11.23 microdeletion. The phenotype associates vasculopathy (arterial stenosis, hypertension), dimorphism and intellectual disability. Microdeletion includes several genes: ELN encodes for elastin and the haplo-insufficiency (only 1 functional copy) causes vasculopathy.

The primary objective is to quantify plasma and urinary levels of elastin peptides in Williams-Beuren patients and 7q11.23 micro-duplication syndrome patients in order to correlate the levels of these markers with the number of copies of ELN gene (proportional positive relationship "gene copy number - circulating levels of markers) Materials and Methods: This prospective study will be carried out in Lyon at the "Hôpital Femme-Mère-Enfant" for 2 years. 3 groups of patients will be studied: Williams-Beuren patients (N=20), micro-duplication 7q11.23 syndrome patients (N=10) and healthy patients (N=60). Subjects will be followed for 1 day.

Clinical examination (weight, height, blood pressure) and biological sample collection (blood and urine sample) will be carry out for Williams Beuren and micro-duplication 7q11.23 patients group. A large majority of visits will be part of patients' usual care. A large part of patients are systematically seen in consultation once a year. For healthy group, only biological sample collection will be carry out. The PE concentrations will be assessed and compared between the three groups of patients.

Inclusion Criteria:

• Age : from 3 months to 60 years old
• Williams Beuren group : Diagnosis confirmed with FISH
• Micro-duplication 7q11.23 group : Diagnosis confirmed with CGHarray
• Healthy Group : no cardiovascular and neurological medical history
• Informed consent

Exclusion Criteria:

• No social insurance
• Subject under judicial protection
• Subject participating in another research including an exclusion period still in progress