MNGIE is an uncommon, autosomal recessive multisystem disorder, caused by loss of function of mutations in the TYMP/ECGF1 encoding for thymidine phosphorilase (TP). MNGIE phenotype is characterized by gastrointestinal disorders, peripheral neuropathy, ophtalmoplegia and leukoencephalopathy. We report a clinical case of a 23 year old female, affected by MNGIE and submitted to allogeneic hematopoietic stem cells transplantation (HSCT). At the first nutritional status examination, weight was 36 Kg, BMI was 15 Kg/m2 and bioimpedance showed a protein-caloric malnutrition. The clinical history revealed asthenia, abdominal pain, headache and amenorrhea. Her diet was unbalanced and insufficient. We elaborated a balanced and hyper caloric diet with a protein supplementation (10 g/day) with a concentrate of isolated whey proteins with high soluble cysteine content and a plant-based superoxide dismutase (SOD). Follows up were planned monthly, then after 3 months and the prescribed calorie intake was finally reached with a gradual improvement of her nutritional status. After one year and a half, weight was 40,5 Kg, BMI was 16,9 with an improvement of blood tests, BIA and muscle strength. Clinically the patient reported a significant improvement of asthenia, fatigue and of abdominal pain but amenorrhea persisted. Patients affected by MNGIE and submitted to HSCT improve their clinical status but malnutrition often persists. Nutritional counselling can positively affect clinical course of this disease, considerably improving body composition and symptoms.