IVR researchers investigated the relationship between mutation proportion and disease severity in MELAS. This research was published in Human Molecular Genetics (LINK).

This study assayed the proportion of mitochondria carrying the m.3243G mutation versus those carrying the m.3243A wildtype allele in blood and dermal fibroblasts.
The m.3243G mutation in the mitochondrial genome is a common cause of retinal degeneration in patients with MIDD (maternally inherited diabetes and deafness), MELAS (mitochondrial encephalopathy, lactic acidosis and stroke-like episodes), and Leigh syndrome. A increase in proportion of mitochondria harboring the mutant allele was significantly correlated with earlier onset of visual symptoms, but not increased severity of the visual symptoms. These results show that precise measurement of m.3243G proportion in clinically-accessible tissues can yield important information for management of the associated disease.