Multiple mtDNA deletions in Kearns‐Sayre syndrome associated with macular dystrophy

Abstract

AbstractPurpose Kearns‐Sayre syndrome (KSS) is a rare disorder resulting from a mitochondrial dysfunction. Classical triad includes chronic progressive external ophthalmoplegia (CPEO), tapetoretinal degeneration and complete heart block. A 48‐year‐old woman with a clinically and histopathologically confirmed KSS developed a maculopathy resembling an adult‐onset vitelliform macular dystrophy in her right eye.Methods The patient underwent optical coherence tomography (OCT), fluorescein angiography (FA),electroretinogram (ERG), electrooculogram (EOG), visually evoked cortical potentials (VEP)and muscle enzymes determination. A sartorius muscle biopsy was performed. DNA was submitted to Southern blot analysis.Results The foveal vitelliform lesion remained hypofluorescent because the accumulation of vitelliform material blocks fluorescence. OCT revealed a retinal pigment epithelium (RPE)detachment in the right macula. ERG, EOG and VEP were normal. Serum lactate value was 3.3 mg/dL (normal: 0.63‐2.44). Muscle enzymes were normal. Muscle biopsy demonstrated "ragged red fibres" on Gomori‐trichome staining. On electron microscopy abnormal aggregation of large and atypical mitochondria were observed. DNA analysis identified the presence of multiple deletions in the mtDNA of a muscle sample, with the common deletion of 4977 bp the most abundant.Conclusion The retina, in particular RPE, is highly vulnerable to mtDNA defects and decreased oxidative phosphorylation. This is the first report associating KSS to multiple mtDNA deletions and there have been no previous reports of such macular lesion occurring in association with KSS.Ohthalmologists should be aware of the mitochondrial ocular myopathies.