Abstract
Purpose: :
To report ocular findings in the mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS syndrome) in a family with MTTL1 mutation.
Methods: :
Each patient underwent full ophthalmic examination after providing informed consent. Full-field (ff) ERG was performed with contact lens recording electrodes and incorporated the ISCEV Standards. Further tests performed included multifocal (m) ERG according to the ISCEV guidelines, fundus autofluorescence imaging (FAI), optical coherence tomography (OCT) and fundus fluorescein angiography.
Results: :
A 30 year-old man developed ataxia and mioclonal epilepsia. He presented six stroke-like episodes in the last 2 years. He showed a myopathic pattern on EMG and ragged-red fibers on muscle biopsy. Ophthalmic evaluation disclosed yellow lesions in the macula resembling an adult-onset vitelliform macular dystrophy and peripheral pigmentary retinopathy in his both eyes. FAI showed increased hyperfluorescence with presumed lipofuscin accumulation. OCT demonstrated accumulation of material in the sub-neurosensorial retinal space; the photoreceptor and outer plexiform layers thickness were irregular at the extrafoveal region, where there was deletion of the MLI. ffERG had diminished scotopic and photopic responses. mfERG revealed central and peripheral reduction of function.Her sister was a 21-year-old woman with sensorineural deafness since 9-year-old. RNM, EMG and muscle biopsy were normal. She presented no ophthalmic symptoms. Full-field ERG was supranormal. mfERG revealed central preservation of function and reduction of function in the periphery . FAI was normal. OCT revealed extrafoveal deletion of the MLI and irregular thickness of the photoreceptor and outer plexiform layers.Their mother presented sensorineural deafness, cardiomiopathy and diabetes. She was suddenly dead at 45 years old.
Conclusions: :
MELAS syndrome is a genetically heterogeneous mitochondrial disorder with a variable clinical and ophthalmic phenotype, as we present herein.The retina, in particular the retinal pigment epithelium, is involved by MTTL1 defect, and patients with MELAS phenotype should be examined for the presence of retinal manifestations, even if they are asymptomatic. The supranormal ERG responses suggests that MTTL1 may also interfere hyperpolarizing bipolar cells function. Hipernormal ERG’s have been associated with cone distrophy in humans as well as in mtDNA Ant1-deficient mice. On the other hand, there have been no previous reports of such vitelliform macular lesion occurring in association with MELAS syndrome.
Keywords: retinal degenerations: cell biology • mitochondria • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)