The A to G point mutation at position 3243 of the mitochondrial DNA tRNALeu(UUR) gene is commonly found in patients with the syndrome of mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS). A male patient was referred at 7 months with failure to thrive, developmental delay, microcephaly and hypotonia since age 2 months. He had developed lactic acidosis and increasingly frequent seizures since age 5 months. The patient was admitted at 15 months with pleural and pericardial effusions, which resolved. Three weeks later he developed evidence of pancreatitis with hyperglycemia, sudden profound increase in lactic acidosis and increased serum lipase. He died unexpectedly the next day of cardiorespiratory collapse following an acute gastro-intestinal hemorrhage. Analysis of mitochondrial DNA (mtDNA) in muscle showed heteroplasmy for the mutation MTTL1*MELAS3243G (> 95%). Infants with this mutation commonly present with failure to thrive, significant developmental delay, and hypotonia, while stroke-like episodes occur later in survivors. They usually have lactic acidosis and a high percentage of mutant mtDNA in muscle.
Conclusion: Respiratory chain disorders including the mtDNA MTTL1*MELAS3243G mutation should be suspected in infants with this systemic and neurologic presentation. Pancreatic dysfunction, both acute and chronic, needs to be added to the list of symptoms of disorders of the respiratory chain.