An Atypical SURF1 -Associated Leigh Syndrome Phenotype Presenting with Ocular Dyspraxia and Nocturnal Disturbances

Background: Leigh syndrome is an uncommon mitochondrial neurodegenerative disease resulting from impaired cellular energy production, particularly abnormalities affecting oxidative phosphorylation. Among the nuclear genes implicated in the disorder, SURF1 is a recognized cause of childhood-onset disease and is frequently associated with lesions affecting the brainstem. Objective: This case report presents an unusual clinical phenotype of genetically confirmed SURF1 -related Leigh syndrome, with particular emphasis on ocular dyspraxia and clinically significant disturbances occurring during sleep. Materials and methods: Clinical records from a pediatric patient investigated for a suspected mitochondrial disease were retrospectively examined. The evaluation included neurological assessment, metabolic investigations, electrophysiological studies, serial brain magnetic resonance imaging, and molecular genetic testing. Whole-exome sequencing was performed to establish the underlying genetic diagnosis. Results: A 4-year-and-10-month-old boy was found to carry a homozygous pathogenic variant in SURF1. His clinical course was characterized by progressive motor deterioration, brainstem dysfunction, ocular dyspraxia, and recurrent nocturnal disturbances. Magnetic resonance imaging demonstrated symmetric bilateral abnormalities affecting the brainstem and pyramidal pathways, findings compatible with Leigh syndrome. Lactate levels remained persistently elevated, ranging from 2.7 to 8.6 mmol/L. The coexistence of ocular dyspraxia and prominent sleep-related symptoms represents an uncommon clinical pattern within the SURF1 -related Leigh syndrome spectrum. Conclusion: The present case contributes to the expanding clinical spectrum associated with SURF1 -related Leigh syndrome. It also emphasizes the value of careful assessment of ocular motor function and sleep behavior when evaluating children with suspected mitochondrial disease.