 The purpose of this study is to find out if a stem cell transplant is safe for patients with a very rare disease. The stem cell transplant is called AHSCT for allogeneic hematopoetic stem cell transplantation. The rare disease is called MNGIE for Mitochondrial NeuroGastroIntestinal Encephalomyopathy. Patients with MNGIE will be transplanted with stem cells from an individual who is human leukocyte antigen HLA 1010 matched. The purpose of the transplant is the production of thymidine phosphorylase. 