METHODS: Prospective multicentric clinical trial including 7 French pediatric intensive care units. Serial cardiac ultra sounds and blood sampling will be done for patients hospitalized for purpura fulminans beginning at the time of admission in pediatric intensive care. Any child from 6 months to 18 years without preexisting cardiac disease and presenting with purpura fulminans will be enrolled after obtaining consent of both parents. From adult's studies on septic shock and BNP, a total number of 30 patients was calculated to be necessary to prove the interest of BNP in this indication.