Unusual ocular and renal phenotype of MELAS syndrome with maculopathy associated with focal and segmental glomerulosclerosis. 

Background: Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a maternally inherited genetic mitochondrial disorder. Case presentation: We present the clinical case of a 28-year-old woman with nephrotic proteinuria and vision loss. Bilateral macular oedema and drusen-like deposits were observed in the funduscopic examination and coincided with the first episode. She presented with renal function deterioration. Furthermore, the renal biopsy revealed focal and segmental glomerulosclerosis. The genetic study was negative, and complete sequencing of mitochondrial DNA was requested. The results indicated, 45% heteroplasmy for the pathogenic variant m.3243A>G in the MTTL1 gene, which is compatible with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome. Conclusions: : Therefore, our clinical case highlights the clinical heterogeneity of this syndrome, as this patient presented with exceptional renal and ocular involvement without damage to other organs that are usually affected. These phenotypes are not well documented in the literature on MELAS.