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Editor,—Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease characterised by acute bilateral loss of central vision.1 We report a patient with LHON who had elevated lactate and pyruvate levels in blood and cerebrospinal fluid (CSF).
A 22-year-old man noticed blurred vision in both his eyes. Corrected visual acuity was 0.04 in his right eye and 0.05 in his left. Slit-lamp examination and intraocular pressures were normal. Pupillary light reflex was full in both eyes.
Fundus examination revealed slightly hyperaemic optic discs. There was marked disc pallor over the next 2 months. Fluorescein angiography showed diffuse hyperfluorescence in the paramacular area. Goldmann perimetry showed a large central scotoma in each eye. No detectable responses of pattern visually evoked potentials were observed. His neurological examination, magnetic resonance imaging (MRI) of the brain, electromyography, and electroencephalography were normal. The resting blood level of lactate was elevated to 15.7 mg/dl (normal 3.3–14.9 mg/dl) and that of pyruvate was elevated to 1.51 mg/dl (normal 0.30–0.94). The level of lactate in the CSF was 13.8 mg/dl (normal 8.7–13.5), and level of the pyruvate was 1.27 mg/dl (normal 0.37–0.75). The blood level of lactate was elevated to 38.0 mg/dl, and the pyruvate level was elevated to 2.26 mg/dl after exercise loading. Biopsy of the biceps brachii muscle showed no ragged red fibres with Gomori trichrome staining. A point mutation of mtDNA at nt11778 was determined in the leucocyte. Neither the mtDNA point mutation at nt3243 (MELAS), nt8344 (MERRF), nor large deletion (KSS, CPEO) was detected.
Previous reports suggested that LHON is a multisystem disorder with various clinical manifestation and abnormal laboratory findings.2 3 Although an abnormal rise of venous lactate is observed in patients with Kearns–Sayre syndrome and other mytochondrial cytopathy, a few reports have demonstrated abnormal elevation of lactate and pyruvate in blood and CSF in LHON.4 Since 11778 mtDNA encodes subunit 4 of complex l,5 one would expect that the 11778 mtDNA mutation causes an amino acid change in mitochondrial respiratory chain and leads to impaired catabolism of lactate and pyruvate. The resting lactate and pyruvate levels in blood and CSF and those after aerobic exercise would give additional information on the biochemical abnormalities of LHON.
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