1. Patient under guardianship or curatorship 2. Patient with plausible alternate diagnosis 3. ARDS evolving for more than 4 days 4. Contraindication to the HCQ 5. Contraindication to DXM 6. Uncontrolled septic shock 7. Untreated active infection or treated less than 24 hours 8. Long-term patient treated with corticosteroids (> 20 mg / day) or HCQ 9. Immunocompromised patients: AIDS, bone marrow or solid organ transplant recipients 10. Pregnant women

1. Patient under guardianship or curatorship 2. Patient with plausible alternate diagnosis 3. ARDS evolving for more than 4 days 4. Contraindication to the HCQ 5. Contraindication to DXM 6. Uncontrolled septic shock 7. Untreated active infection or treated less than 24 hours 8. Long-term patient treated with corticosteroids (> 20 mg / day) or HCQ 9. Immunocompromised patients: AIDS, bone marrow or solid organ transplant recipients 10. Pregnant women