BACKGROUND: The aim of this paper is to describe the clinical features and 
molecular findings of a unique case of Leber's hereditary optic neuropathy 
(LHON)/mitochondrial encephalopathy, lactic acidosis and stroke-like episodes 
(MELAS) overlap syndrome presenting as nonischemic central retinal vein 
occlusion (CRVO).
METHODS: An 11-year-old Chinese girl presented with sudden onset of bilateral 
blurred vision. The clinical history, imaging studies, and molecular analysis 
results were reviewed. The PubMed and OVID databases were used for literature 
review.
RESULTS: Nonischemic CRVO in the subject's right eye and tortuosity of small and 
medium-sized retinal arterioles in the left eye were found at initial 
presentation. Bilateral optic disc pallor was then noted with recovery of CRVO. 
Severe headache and several stroke-like episodes occurred subsequently, with 
elevated lactate levels in serum and cerebrospinal fluid. LHON/MELAS overlap 
syndrome was diagnosed, and mitochondrial DNA sequencing revealed G13513A 
heteroplasmic mutation. Vision was 20/30 in the right eye and 20/800 in the left 
eye at the last visit.
CONCLUSIONS: Mitochondrial DNA G13513A mutation can cause LHON/MELAS overlap 
syndrome. Nonischemic CRVO is a rare manifestation of LHON/MELAS. Atypical 
findings in cases of LHON should raise the suspicion of overlap syndrome or 
other mitochondrial diseases.