We present a patient with ataxia, retinitis pigmentosa, dysarthria, neurosensorial deafness, nystagmus and leukoencephalopathy. A novel heteroplasmic G to A transition at nucleotide 15975 was found, affecting the T arm of the mitochondrial (mt) tRNAPro gene. A biochemical analysis of respiratory chain enzymes in muscle revealed isolated complex I deficiency. This is the fourth pathogenic tRNAPro point mutation to be associated with an mt disorder. The result highlights the importance of molecular dissection of mtDNA in patients with defined mt disorder and confirms the clinical and biochemical heterogeneity associated with tRNAPro mutations.
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