Mutation in the deoxyguanosine kinase gene (DGUOK) results in hepatocerebral form of mitochondrial DNA (mtDNA)-depletion syndromes (MDS) . Affected individuals have early progressive liver failure, neurological abnormalities, hypoglycaemia and lactic acidosis. Majority of affected individuals die within the first year of life. Although hypoglycaemia is a consistent feature of hepatocerebral form of MDS, there is a single report of biochemical hyperinsulinism as the underlying cause with pancreatic islet cell hyperplasia on autopsy in two patients.