The mitochondrial A3243G mutation presenting as severe cardiomyopathy

A 6 year old Portuguese boy with dilated cardiomyopathy had abundant ragged red fibres in muscle (20% of total) and severe lactic acidosis. Molecular genetic analysis showed the A to G transition in the mitochondrial transfer RNA(Leu(UUR)) gene at nt 3243 ('MELAS mutation'), which accounted for 88% and 68% of the total mtDNA in his muscle and blood, respectively. Molecular studies in blood from 16 maternal relatives identified lower percentages of the mutation only in the oligosymptomatic mother and brother. This case reinforces the notion that cardiomyopathy can be the presenting and predominant clinical expression of the A3243G mutation.