The histological and immune-histological findings of islet cells in two patients with mitochondrial diabetes, one with MELAS syndrome and the other with MERRF syndrome. They observed that the severity of diabetes correlated with the histological findings on autopsy. However, the authors raise several concerns regarding the conclusions drawn. They argue that the differences in histology could be attributed to the distinct genotypes of MELAS and MERRF, rather than solely reflecting the severity of diabetes. They also suggest that other factors such as heteroplasmy rates, mtDNA copy numbers, and the presence of co-morbidities should be considered. Additionally, they question whether atrophy of islet cells necessarily indicates reduced insulin production and call for further investigation into serum insulin and C-peptide levels. Overall, the study highlights the need for a more comprehensive understanding of the genetic and clinical factors influencing diabetes severity in mitochondrial disorders.