RecruitingThe Natural History Study of Mitochondrial NeuroGastroIntestinal Encephalopathy (MNGIE)This is a multi-center natural history study of Mitochondrial NeurogastroIntestinal Encephalopathy (MNGIE). Patients will be followed over time to assess clinical symptoms. The investigators hope to learn more about the disease of MNGIE as well as develop useful measures of disease status for use in future clinical trials. Additional clinical centers will be listed as they become available.