In this case report, a 23-year-old normal-functioning young man was repeatedly admitted to the hospital with mal-nutrition and pseudo-obstruction. External ophthalmoplegia, global muscular atrophy and demyelinating sensory-motor-autonomic neuropathy became evident. An MRI showed symmetrical white matter lesions and muscle biopsy atrophic muscle fibres. A TYMP mutation confirmed the diagnosis, and the patient had a rapidly fatal disease course. Mitochondrial neuro-gastro-intestinal encephalo-myopathy is rare and often overlooked. In less advanced disease, stem cell transplantation can correct thymidine phosphorylase deficiency.