Novel POLG mutation in a patient with early-onset parkinsonism, progressive external ophthalmoplegia and optic atrophy

Introduction: Mitochondrial DNA polymerase gamma (pol gamma) encoded by POLG plays an indispensable role in the process of mitochondrial DNA replication and repair. The mutation of POLG can result in mitochondrial dysfunction leading to a broad spectrum of disease. Methods: We report a 29-year-old Chinese female presented with levodopa-responsive parkinsonism, external ophthalmoplegia and optic atrophy. We conducted clinical, molecular iconographic, histological and genetic analyses on this patient. Results: Sequencing of the POLG gene revealed compound heterozygote mutations of a novel c.2693T > C (p.I898T) mutation in exon17 and c.2993C > T (p.S998L) in exon19. The mutation c.2693T > C (p.I898T) has never been reported. Also our patient's cardinal symptoms are rare and different from other cases which have been reported. Conclusion: This finding of ours has broadened the spectrum of phenotype caused by the mutation of POLG.