Cohort Analysis of Clinical and Biological Severe Childhood Asthma

Inclusion Criteria: Children with severe asthma: * Child aged 3 to 12 years * Asthmatic child who, despite treatment with a combination of inhaled corticosteroids (at least 800 mcg / day equivalent Beclomethasone) bronchodilators and long-acting or properly taken daily leukotriene or short acting nebulized bronchodilators (inhaler technique and compliance verified) presents one of the criteria following: * Persistence of symptoms or chronic use of bronchodilators short duration of action at least three times a week for at least 3 months * exacerbations in the previous year: * at least one care unit admission or continued resuscitation * at least two hospitalizations for acute severe asthma requiring IV therapy * at least 2 courses of oral corticosteroids for exacerbations * post BD FEV \<80% or UARS post BD\> 150% predicted * Signature of consent or the holder (s) of parental authority * Particular case of patients treated with Xolair® : Patients currently receiving Xolair® but who met the severity criteria of asthma, as described above, before the start of treatment with Xolair® are includable. Children with non-severe asthma: Inclusion Criteria * Child aged 3 to 12 years * Controlled without treatment or with low doses of inhaled corticosteroids (\<500 mg / day beclometasone equivalent) asthma * Child with normal EFR (Child over 4 years) * Child who did not have more severe exacerbation (assessed taking oral corticosteroids) in the previous year * Child not admitted in the previous year for asthma. * Signature of consent or the holder (s) of parental authority Exclusion Criteria: * Child with bronchopulmonary dysplasia * Child with severe sequelae of viral infections * Refusal of the child or parents Data collection for research and follow up of patients : tests carried out in the 3 months prior to inclusion are used Blood sample for DNA extraction and the biobank: for young children, sampling at least 4 to 5 ml on dry tubes for serum and 6 ml at least for DNA. These samples should be stored at room temperature, transported within 48 hours to biological resources (CRB) Necker E,fa,ts Malades.