Background To describe the ophthalmological manifestations in patients with childhood onset Leigh syndrome (LS) and investigate the correlation between genotypes and phenotypes in patients with LS.

Methods Childhood onset LS was clinically and enzymatically confirmed in a total of 63 patients. Among them, 44 patients who underwent ophthalmologic consultation were included in this study. Patients with LS underwent genotyping for the whole genome of mitochondrial DNA and SURF1 mutations. The clinical demographic and ophthalmologic phenotypes were compared between the good prognosis group and the poor prognosis group.

Results Strabismus (40.9%) was the most frequently observed ophthalmologic manifestation, followed by pigmentary retinopathy (22.5%), optic atrophy (22.5%), ptosis (15.9%), and nystagmus (13.6%). Thirteen patients were exotropes and five patients were esotropes. The mean exodeviation was 29.6±12.5 prism dioptres (PD) and the mean esodeviation was 24.0±8.9 PD. All patients with esotropia reported disease onset at <1 year old. Among 26 patients older than 4 years, eight (30.8%) patients had better than 0.4 in the best eye was noted. Eyelid ptosis was a main presenting sign in four patients (9.1%). Among these patients, two patients had m.13513G>A mutation in the MT-ND5 gene. Age at onset was 2.47±2.06 years in the good prognosis group and 0.92±0.98 years in the poor prognosis group (p=0.002). Serum lactate peak concentration was 3.23±1.36 mmol/L in the good prognosis group and 4.54±2.31 mmol/L in the poor prognosis group (p=0.051).

Conclusions LS is a group of mitochondrial disorders with variable ophthalmologic manifestations, the most frequent being strabismus in this study. Ptosis could be an initial sign in patients with LS and these patients can be easily misdiagnosed as having juvenile myasthenia gravis.