Antibiotic Treatment and Intravenous Immunoglobulin Trial for PANDAS

An increasing body of evidence indicates that an immune basis might underline a number of pediatric neuropsychiatric disorders. Research studies found a subgroup of children who had Obsessive compulsive (OCD) and/or tic disorders following a Group A beta-hemolytic streptococcal (GAS) infection. The subgroup is identified by the acronym, PANDAS (pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections. More recently, several PANDAS variants have been described, including adult-onset variant. There are many evidences that OCD/tic symptoms could be due to an immunologic reaction against brain tissues following a streptococcal infection. The purpose of this study is to know if sertraline (one of the SSRI approved by FDA to improve OCD/tic symptoms in these patients) plus antibiotic (benzathine penicillin G or azithromycin in case of penicillin allergy) is more effective than SSRI only. Patients who will not respond to antibiotic will be treated with intravenous immunoglobulin (IVIG) in order to inactivate the immune reaction versus brain tissues.(No treatment response is based on the lack of a Y-BOCS score improvement of at least 35%). Objectives: * To determine the safety and efficacy of SSRI+AB compared to SSRI only. * To test the safety and additional beneficial effects of high dose of IVIG on antibiotic prophylaxis for the treatment of OCD symptoms in non-responders patients with PANDAS. Study methodology: * Participants will be screened to obtain medical history and other information at Neurologic and Psychiatric Sciences Department of Florence University Hospital and at Paris-est University. * Participants will receive a treatment of either SSRI+AB or SSRI+placebo for 12 weeks (double-blind randomized trial) * Patients who will not respond to AB will be admitted to the hospital to receive IVIG for 5 days, for 5 consecutive months. * Follow-up visits will take place 3 and 6 months after the first evaluation, followed by 6 month