Novel cluster of tRNA(Leu(UUR)) mutations in a sporadic case of infantile myopathy restricted to muscle tissue

In a previous study we reported on a case with severe infantile, mitochondr ial myopathy caused by somatic mutation [12]. in the present study we give evidence for asymmetric tissue distribution of the mutations. Mitochondrial DNA (mtDNA) analysis showed a cluster of nearly homoplasmic point mutation s in the tRNA gene for leucine (UUR) (A3259 G, A3261 G, A3266 G, A3268 G). The mutation is abundant in muscle, but is not found in blood cells. This c luster of mutations is sporadic, because the search for mutant molecules in the blood of the healthy mother and maternal grandmother did not show thes e alterations.