Pediatric Crohn's Disease AdalImumab Level-based Optimization Treatment (PAILOT) Trial

Eligible patients are those who are planned to start Adalimumab (ADA). Patients will be randomized at the first screening visits to either group 1 (interventional) or group 2 (clinical). Eligible patients, will start induction treatment (weeks 0,2) with ADA (\> 40kg 160/80/40 mg every 2 weeks or \< 40 kg 100/50/25 mg for m2 body surface area every 2 weeks). Interventions will start from the 4th injection for responding patients only (based on levels taken prior to the third injection). Responding patients will continue to the maintenance phase in which they will receive ADA every 2 weeks, either 40 mg or 25 mg/m2. At screening, and every 2 months all patients will be examined and have height, weight, PCDAI performed as well as comprehensive laboratory examinations.