A newly recognized type of heart disease, or "cardiomyopathy," caused by an X-linked mutation in the LAMP2 gene, is rapidly progressive, leading to cardiac death in young patients, according to a report in the Journal of the American Medical Association.

The cardiomyopathy in the disorder is known to be clinically similar to severe hypertrophic cardiomyopathy, but the natural history and genetic patterns associated with the disease was unclear, lead author Dr. Barry J. Maroon, from the Minneapolis Heart Institute Foundation, and colleagues note.

In their study, the researchers examined the natural course and outcomes of LAMP2 cardiomyopathy in six boys and one girl, ranging in age from 7 to 17 years.

During an average follow-up period of 8.6 years, left ventricular systolic dysfunction and cavity enlargement developed in the patients. Adverse clinical outcomes included refractory heart failure and death in four patients and sudden death, aborted cardiac arrest, and heart transplantation in patient each.

Marked left ventricular hypertrophy was noted in the group, which included massive ventricular septal thickening in two subjects, the authors note. ECG findings included pronounced increased voltages of R-wave or S-wave as well as deeply inverted T-waves.

At autopsy, the histopathologic features were similar to those of a lysosomal storage disease and to hypertrophic cardiomyopathy, the researchers report.

The resemblance of LAMP2 to other types of cardiomyopathy "underscores the necessity and power of timely genetic testing in young patients" who have a substantially enlarged left ventricule, for the early molecular identification of this myocardial storage disease characterized by adverse clinical course," the authors conclude.

They add: "These observations also raise legitimate consideration for early intervention with heart transplantation ... despite the possibility of extracardiac organ involvement in this disease."