Abstract

FR.20.07

Mitochondrial A3243G point mutation associated with pigment epithelial atrophy and hypoacusis in a monocygotic pair of twins.

Till Oppermann, Johann Roider, Jost Hillenkamp

Augenklinik, Campus Kiel, Universitätsklinikum Schleswig-Holstein, Kiel

Objective
Mitochondrial A3243G point mutations cause variable pathologic changes in different organs. A combination of diabetes mellitus with deafness (maternal inherited diabetes and deafness, MIDD) and retinal pigment epithelial (RPE) atrophy has been described.
Methods
Medical history, best corrected decimal visual acuity (BCVA), indirect funduscopy, automated 30° threshold perimetry, fundus autofluorescence and mitochondrial tRNA sequencing were performed in a pair of monozygotic twins.
Results
Both 47 year old female patients complained of hypoacusis since 20 years and 7 years, respectively, and visual impairment since 3 years. There was no family history of hereditary diseases, and no diabetes. In one twin, BCVA was 0.8 in the right and 0.6 in the left eye. In the other twin BCVA was 1.2 in the right and 0.7 in the left eye. Visual field testing showed similar, almost symmetrical absolute central and paracentral scotomas in both patients. Funduscopy revealed sharply demarcated central areas of atrophy of the RPE which corresponded to the visual field defects. Fundus autofluorescence was reduced in the areas of RPE-atrophy, but showed granular hyperfluorescence of the adjacent RPE. The areas of atrophy had slightly enlarged over the past 2 years. Audiometry revealed hypoacusis. In both patients, RNA sequencing confirmed a heteroplasmic mitochondrial point mutation at the A3243G locus.
Conclusions
Heteroplasmic mitochondrial mutations may cause variable changes in different organ systems. However, the ocular phenotype in the described pair of twins was almost identical. Fundus autofluorescence showed little progression of the RPE atrophy.

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