MPV17 mutation-related mitochondrial DNA depletion syndrome: A case series in infants

MPV17 is a mitochondrial inner membrane protein, involved in transporting deoxynucleotides into the mitochondria. Pathogenic MPV17 mutations can cause mitochondrial deoxyribonucleic acid (DNA) depletion syndrome, which has a varied presentation with neurological, muscular and hepatic involvement. Presentation as liver failure is relatively uncommon. Here, we report four infants from four separate families with pathogenic, homozygous MPV17 mutations. All had predominant hepatic involvement with cholestasis, lactic acidosis and hypoketotic hypoglycemia. Three of them had presented with liver failure. Interestingly, one of them showed fluctuating liver functions, which worsened with infection and improved after aggressive treatment with antibiotics and supplements. Two of the four cases died in infancy, while the other two improved on conservative management with medium-chain triglyceride-based diet, vitamin supplements, co-enzyme Q and carnitine. The two surviving children are alive at 12 and 25 months of age with native liver with normal to mildly deranged liver function and no neurological dysfunction. Next-generation sequencing confirmed the diagnosis in all of our cases. One of the detected mutations, c.55delC (p.Gln19ArgfsTer3) is a novel pathogenic frameshift mutation, while another mutation c.388G>C (p.Ala130Pro), which was previously reported in Single Nucleotide Polymorphism Database in heterozygous form, is being predicted as likely pathogenic in our case series. We, therefore, propose mutation testing for MPV17 gene during evaluation of indeterminate infantile liver failure, especially those with hypoglycemia and raised plasma lactate.