Mammoth ventricular hypertrophy.

A 23-year-old man was referred to the cardiology clinic because of an abnormal ECG and a murmur. He was asymptomatic from the cardiac perspective, and there was no significant family history of cardiac disease or sudden death. He was physically active but was not an athlete and did not exercise regularly. On physical examination, he had a blood pressure of 140/70 mm Hg in both arms with a normal jugular venous pressure of 8 cm water. Cardiac auscultation revealed a soft crescendo-decrescendo systolic murmur heard loudest over the lower left sternal edge. The rest of the physical examination was normal. His ECG showed sinus rhythm with markedly increased voltages suggestive of left ventricular hypertrophy (Figure 1). His echocardiogram was of very limited quality as a result of poor acoustic windows but was suggestive of left ventricular hypertrophy. Cardiac magnetic resonance cine imaging showed striking mammoth asymmetrical left ventricular hypertrophy with preserved systolic function (Figures 2–4 and Movies I and II in the online-only Data Supplement). The basal septum measured 5.8 cm at its maximum dimension compared with 2.0 cm at the basal inferolateral wall. There was also severe right ven-tricular hypertrophy with a basal free wall dimension of 1.3 cm. Late-gadolinium-enhancement imaging demonstrated extensive patchy hyperenhancement throughout the myocardium (Figures 5–7 and Movie III in the online-only Data Supplement). A 24-hour Holter monitor showed sinus rhythm throughout. The differential diagnosis of mammoth left ventricular hypertrophy in adults includes Danon disease, mutations in the gene for the PRKAG2 subunit of adenosine mono-phosphate–activated protein, and sarcomeric hypertrophic cardiomyopathy. However, the extensive late-gadolinium-enhancement pattern seen in this patient is not typical of sar-comeric hypertrophic cardiomyopathy, which usually shows a patchy midwall distribution with predilection for the anterior and posterior right ventricular insertion sites. Danon disease is a glycogen storage disease caused by mutations in the X-linked lysosome-associated membrane protein (LAMP2) gene. 1 Although noncardiac features such as intellectual impairment and myopathy may be seen in some patients, it can present with an isolated cardiac phenotype of symmetrical or asymmetrical ventricular hypertrophy with pre-excitation. Moreover, it has been associated with particularly massive left ventricular hypertrophy, including the most substantial hypertrophy reported in humans (60–65 mm). 1 Early diagnosis is vital because Danon disease leads to a lethal cardiomyopathy, with few patients surviving beyond the third decade of life. Cardiac transplantation offers the best chance for long-term survival. 2 PRKAG2 mutations also lead to a …