Vitamin D deficiency may be under-diagnosed in sickle cell disease French children. Therefore, the investigator need an epidemiologic study about the prevalence of vitamin D deficiency in this specific population. There are not specific guidelines neither testing nor treatment. The investigator propose to test vitamin D status in all children with sickle cell disease who are consulting their referring haematologist doctor or in the emergency ward.

Inclusion Criteria:

• Children: under 18 years old
• Sickle cell any genetic type homozygous or composite heterozygous
• To receive an assessment independently of the study, during a presentation to the emergency ward and/or a follow-up consultation by the hematologist
• no parental opposition signed by at least one parent/legal representative and no child opposition
• social security beneficiary

Exclusion Criteria:

• History of hematologic grafting

This study will focus on minor patients (0-17 years) with sickle cell disease, currently monitored in the active queue of the Lyon sickle cell reference centre of IHOPe, consulting their referring physician or paediatric emergencies of HFME, and having a blood test independently of the study.