The recently recognized disease is a type of cardiomyopathy, or heart muscle disorder, linked to genetic mutations in the lysosome-associated membrane protein gene (LAMP2). Until now, the natural course of the disease was unclear.
Researchers from the Minneapolis Heart Institute Foundation studied seven people diagnosed with Danon disease when they were 7 to 17 years old. In six of them, diagnosis was made as the result of a heart murmur, family screening and findings on routine electrocardiogram tests or from such symptoms as chest pain and fainting. In one person, atrial fibrillation, an abnormal heart rhythm, led to the diagnosis.
Within nine years of diagnosis, on average, all seven had encountered serious problems. One person had a heart transplant, and four died of acute or progressive heart failure. Their deterioration was often rapid, going from having few or no symptoms to end-stage heart failure within as little as six months.
The other two people in the study had sudden, unexpected, major arrhythmic events, and one of them died suddenly from ventricular fibrillation — very rapid, uncoordinated contractions of the ventricles —that was not controlled by an implantable cardioverter defibrillator.
All seven developed problems with contraction of their left heart ventricle, called left ventricular systolic dysfunction. All seven had a defibrillator implanted, but in five of them, the devices failed to prevent lethal tachyarrhythmias — excessively rapid heartbeat accompanied by irregular heartbeat.
The final electrocardiograms examined by the researchers showed significant enlargement of the left ventricle in all seven, the study reported.
“The clinical course of these seven patients with LAMP2 mutations provides important insights regarding molecular diagnosis as well as the natural history, pathophysiology and clinical implications of this recently recognized genetic cardiomyopathy,” the researchers wrote. “LAMP 2 mutations cause a particularly profound and accelerated cardiac disease process characterized by clinical deterioration and early death, perhaps representing one of the most lethal cardiomyopathies in young and usually male patients. Such an outcome occurred in the patients in our study, despite application of the most contemporary treatment strategies.”
The finding “establishes the importance of molecular diagnosis and underscores the utility of genetic testing,” they concluded.
The study is in the March 25 issue of the Journal of the American Medical Association.
The American Heart Association has more about cardiomyopathy.
— Robert Preidt
SOURCE: JAMA/Archives journals, news release, March 24, 2009
Last Updated: March 24, 2009
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