Asymptomatic young man with Danon disease.

Danon disease is a rare, codominant X-linked genetic disorder characterized by the triad of left ventricular hypertrophy, mental retardation, and peripheral myopathy. This disease is caused by mutations in the gene that encodes lysosomal associated membrane protein 2 (LAMP2), a deficiency of which results in the accumulation of autophagic granular débris within the vacuoles of muscle cells. This is a report of an asymptomatic 19-year-old man with Danon disease in the absence of mental retardation or clinically significant skeletal myopathy. This case underscores the importance of accurate diagnosis of unexplained left ventricular hypertrophy, in order to establish an appropriate treatment plan and to advise genetic counseling.