Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a multi-system disorder caused by several homozygous or compound heterozygous mutations, mostly in the nuclear gene of TYMP. Our current knowledge on the underlying pathology of the disease is derived through the study of about 200 cases of different ethnicities. Clinical presentations include severe cachexia, weakness, ptosis, diplopia, abdominal cramps or digestive tract disorders, hearing impairment, and paresthesia.Herein, we aim to present five novel mutations of the nuclear gene of TYMP in six Iranian patients diagnosed with MNGIE. In our population, age at the time of diagnosis was 18 to 49 years, while the onset of the symptoms varied from 13 to 20 years. We detected two pathogenic non-frameshift nonsense premature stop codon mutations (c.1013C > A, and c.130C > T), one variant of uncertain significance (VUS) non-frameshift missense mutation (c.345G > T), one likely pathogenic frameshift insertion (c.801_802insCGCG), and one likely benign homozygous non-frameshift deletion (c.1176_1187del) from two siblings. Our findings also confirm the autosomal recessive inheritance pattern of MNGIE in the Iranian population. The lack of knowledge in the area of nuclear gene-modifier genes shadows the genotype-phenotype relationships of MNGIE.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a rare autosomal recessive disorder. The mutation in the ECGF1 gene causes severe deficiency of thymidine phosphorylase (TP), which in turn increases thymidine and deoxyuridine in the blood, serum, and tissue. The toxic levels of these products cause malfunction of the mitochondrial respiratory chain and mitochondrial DNA. Commonly, patients become symptomatic between 15 and 20 years of age (range 5 months to 35 years). The most commonly affected systems are gastrointestinal, followed by ocular, and nervous system. The disease is often fatal; high mortality rate is reported between 20 and 40 years of age. Treatment modalities that can increase thymidine phosphorylase activity and decrease thymidine and deoxy-uridine have shown symptomatic improvements in patients with MNGIE. Platelet transfusion, hemodialysis, peritoneal dialysis or allogeneic hematopoietic stem cell transplantation (HSCT) have been tried. The survival and long-term benefits of these measures are still not clear. Engrafted patients after stem cell transplantation have showed improvements in serum thymidine and deoxyuridine. We are reporting a case of MNGIE from Saudi Arabia, who underwent allogeneic hematopoietic stem cell transplantation. No MNGIE case has been previously reported from Saudi Arabia or the Gulf Arab countries. From the available literature, so far only 11 patients with MNGIE have undergone stem cell transplantation.