This project will make it possible to better understand the natural history of Cohen Syndrom and the phenotypes associated with mutations in the VPS13B gene, to improve the therapeutic management of patients. It will also provide a better description of Cohen-like syndrome for genetic counselling for the families concerned.

Inclusion Criteria:

• Patients presenting Cohen syndrome and two VPS13B mutations
• who accept a clinical evaluation, and to provide at least one blood sample
• Patients presenting the diagnostic criteria of Cohen syndrome, but without a VPS13B mutation
• Patients presenting neutropenia or pigmentary retinopathy and at least one of the following signs, after exclusion of any other syndrome: mental retardation, microcephaly, truncal obesity

Exclusion Criteria:

• - Patients who do not meet the clinical and/or molecular criteria
• Patients who do not wish to provide a blood sample for question 1,
• Patients who have not provided written informed consent,
• Pregnant or breast-feeding women,
• Persons not covered by National Health Insurance and persons under guardianship or in prison.

Cohen syndrome