RecruitingDrug trialStem Cell Transplantation in Crohn's DiseaseUnfortunately, some patients with Crohn's disease (CD) fail to respond to the best clinical treatments and some only experience temporary benefit. For severe Crohn's disease, there is an experimental treatment called "high dose immunoablation" followed by autologous hematopoietic stem cell transplantation (HSCT). This study removes over active lymphocytes (immunoablation) and replaces them using blood stem cells that have been taken from the patient's own body. The aim of the study is to reset or reprogram the patient's immune system to its state prior to diagnosis.