Danon Disease: The Disease Not Well Understood

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There is a rare genetic condition which causes heart disease (cardiomyopathy), muscle weakness (muscular dystrophy), and mental retardation (or learning problems). It is know as Danon Disease.

Danon Disease was first described in 1981. It affects males more severely than females. When the symptoms of heart disease develop, usually childhood or early adolescence, it progresses rapidly and is usually fatal.

The disease is not well-understood. The natural history and phenotypic expression of this newly recognized disease is incompletely resolved. The study published in the March 25 issue of the the Journal of the American Medical Association is an attempt to shed more light on the disease.

The disease is due to mutations in the X-linked lysosome-associated membrane protein gen (LAMP2). The LAMP2 mutations cause sarcomere protein mutations which lead to the cardiomyopathy and the muscular dystrophy.

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The article reports on seven patients who were diagnosed between the ages of 7 to 17. Six were male and one was female. Only two patients were alive at the end of the study.

All were classified as New York Heart Association Functional Class I at diagnosis. Six were diagnosed on the basis of heart murmur, family screenings, findings on routine ECG, or symptoms of chest pain or syncope. One patient was diagnosed because of atrial fibrillation. Through the 8.6 years of follow-up, all patients were noted to deteriorate rapidly from clinically stable to end-stage heart failure.

All seven developed left ventricular systolic dysfunction and received ICDs, five of which failed to prevent death.

The authors of the study suggest that all young patients who have substantial left ventricular hypertrophy and ECGs with greatly increased voltages and Wolff-Parkinson-White Pattern should be suspected of having LAMP2 cardiomyopathy. They also suggest that patients with Danon Disease should be considered for early intervention with heart transplantation as a treatment for LAMP2 cardiomyopathy.

Sources:
Clinical outcome and phenotypic expression in LAMP2 cardiomyopathy; JAMA 2009; 301: 1253-1259; Maron B, et al
Danon Disease Organization

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