Mitochondrial disease caused by mutations in mitochondrial DNA (mtDNA) can manifest in very different ways. If only an isolated organ is apparently affected, mtDNA defects might not be considered in the differential diagnosis. Giordano et al (Hum Pathol 2013 Jan 17) described three cases of isolated hypertrophic cardiomyopathy caused by homoplasmic mutations in the MTTI gene coding for mitochondrial isoleucine tRNA. They further described respiratory chain defects in the cardiac tissue. They discuss that a unique symmetric pattern of hypertrophy and without left ventricular outflow tract obstruction is seen on echocardiogram in isolated mitochondrial cardiomyopathies, different from the more common pattern in other forms of hypertrophic cardiomyopathy. This paper emphasizes that mtDNA defects should be considered in isolated hypertrophic cardiomyopathy, especially due to the very important implications for future health maintanence of the affected individual and for familal recurrence.
Hilary Vernon MD PhD