Novel cluster of tRNALeu(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, mitochondrial 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 mutations 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 cluster of mutations is sporadic, because the search for mutant molecules in the blood of the healthy mother and maternal grandmother did not show these alterations.