New Cardiomyopathy
New Cardiomyopathy
Abstract & Commentary
By Michael H. Crawford, MD, Editor
Sources: Cheng Z, et al. Danon disease as a cause of concentric left ventricular hypertrophy in patients who underwent endomyocardial biopsy. Eur Heart J 2012;33:649-656. Maron BJ. A phenocopy of sarcomeric hypertrophic cardiomyopathy: LAMP2 cardiomyopathy (Danon disease) from China. Eur Heart J 2012;33:570-572.
Concentric left ventricular hypertrophy (CLVH) is occasionally unexplained. Thus, these investigators from Beijing, China, sought evidence for Danon disease, a glycogen storage disease, in patients being evaluated for cLVH who underwent endomyocardial biopsy. They identified 50 patients with cLVH defined as a wall thickness on echocardiography of > 13 mm and a ratio of the interventricular septum to posterior wall thickness of < 1.3 in whom there was no obvious cause. On biopsy, 14 of these patients showed classic amyloid disease. The remaining 36 had genetic analysis for the lysosome associated membrane protein 2 (LAMP2) gene and three had a mutation of this gene consistent with Danon disease (8%). The remaining 33 patients had cLVH for uncertain reasons. The Danon disease patients tended to be young males (mean age 15 years) with mild mental retardation and Wolff-Parkinson-White (WPW) syndrome (2/3). All had markedly increased LV voltage on ECG with deep T-wave inversion. Also, all had elevated serum CK, BNP, and hepatic enzymes, but normal troponin levels. All three were still alive and were not hospitalized for cardiac reasons over a mean 20-month follow-up. In addition, all three were NYHA class I and had normal systolic LV function. Their biopsies all showed autophagic vacuoles containing glycogen particles. The authors concluded that Danon disease may explain a significant number of cLVH cases in young men and can be diagnosed by genetic evaluation of the LAMP2 gene.
Commentary
Danon disease should be part of the differential diagnosis of young men with LVH. Although they characteristically have concentric LVH, some have asymmetric septal hypertrophy that resembles hypertrophic cardiomyopathy (HCM). Danon disease is an X-linked dominant disease, unlike HCM. Both can present in young men, but Danon disease patients have a higher incidence of mental retardation (70%), WPW on ECG (2/3), and marked increases in serum hepatic enzymes and CK. Also, very high voltage on the ECG and marked T-wave inversions are often present. Thus, based on the ECG, Danon disease falls into the marked precordial T-wave inversion group, which includes HCM and arrhythmogenic right ventricular cardiomyopathy (ARVC). When this abnormality is found on ECGs done in young men being screened for sports participation, further evaluation is indicated. The prevalence of Danon disease varies with the population studied: 1-4% in all comers with LVH, 6% if HCM and ARVC are excluded, and 8% if amyloid is also excluded. The diagnosis can be confirmed by genetic analysis of the LAMP2 gene. The diagnosis is important because Danon patients have a poor prognosis, dying early of heart failure or sudden arrhythmic death. Interestingly, implantable defibrillators do not always terminate lethal arrhythmias in Danon disease. Thus, early cardiac transplantation is the only effective treatment.
Concentric left ventricular hypertrophy (CLVH) is occasionally unexplained. Thus, these investigators from Beijing, China, sought evidence for Danon disease, a glycogen storage disease, in patients being evaluated for cLVH who underwent endomyocardial biopsy.Subscribe Now for Access
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