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Although mitochondrial (mt) DNA mutation at nucleotide position 11778 accounts for most cases of Leber's hereditary optic neuropathy (LHON), the phenotypic expression may vary greatly even in different members of the same family. The possible influence of exogenous toxicity on phenotypic expression is still debated in LHON. Here we describe 4 siblings carrying the 11778 mtDNA mutation with a different phenotype. The index case developed an atypical optic neuropathy at the age of 60 years after a long history of occupational exposure to polycyclic aromatic hydrocarbons (PAHs). This report underlines a number of unanswered questions about phenotypic variability of LHON including the possible influence of PAH toxicity., (Copyright (c) 2005 S. Karger AG, Basel.)

The authors describe magnetic resonance imaging (MRI) findings in 15 subjects with different clinical stages of Leber's disease. A few and no characteristic abnormalities of the optic nerve signal were found. Nevertheless, MRI can be considered as a useful tool to differentiate optic neuritis together with visual and brainstem auditory evoked potentials.

We report an 8-year-old patient with clinical features suggesting Leigh's syndrome and with a decreased activity of the E1 component of the pyruvate dehydrogenase complex in cultured skin fibroblasts. A nerve biopsy showed the presence of severe peripheral neuropathy, rarely described in the literature. The partial correction of lactic acidosis with oral sodium bicarbonate chronic therapy may result in a slow evolution of the clinical symptoms.

The authors describe the clinical, biochemical, electrophysiological and ultrastructural study of a case of Refsum's disease whose phenotype suggested other hereditary ataxias. Due to the presence of Babinski sign and optic atrophy and the absence of retinitis pigmentosa, this case can be considered atypical. Electrophysiological and ultrastructural findings confirm the variability of peripheral lesions in this hereditary polyneuropathy.