Pigmentary retinopathy in patients with the MELAS mutation 3243A→G in mitochondrial DNA

Background: Our objective was to determine the penetrance of retinal pigment epithelium (RPE) abnormalities and other ophthalmologic manifestations in patients with the 3243A-->G mutation in mitochondrial DNA. Methods: Adult members in two generations were examined from a population-based cohort of 13 pedigrees with 3243A-->G. Twenty-six patients underwent a thorough ophthalmological examination. A chart review was carried out on an additional 44 patients. Results: Paramacular RPE atrophy and areas of hyperpigmentation were found in 10 patients (38%; 95% confidence interval 20-59%). Electroretinography was normal in only one of the eight patients tested, whereas dark adaptation was abnormal in two. RPE abnormalities were associated with more severe clinical phenotypes and higher degrees of 3243A-->G mutation heteroplasmy in muscle. Ten patients had diabetes mellitus, nine of whom had also RPE abnormalities. This finding, however, reflected the severity of the phenotype, and diabetic retinopathy was confidently diagnosed in only two patients. External ophthalmoplegia was detected in occasional patients. Conclusion: RPE abnormalities were found in this population-based cohort at a frequency that was lower than that reported earlier. RPE abnormalities were associated with more severe phenotypes, suggesting that they are expressed in patients with syndromic features. RPE abnormalities and diabetes mellitus co-occurred frequently, but diabetic retinopathy was not common.