A Mild Version of Danon Disease Caused by a Newly Recognized Mutation in the Lysosome-associated Membrane Protein-2 Gene

We present the case of a patient with dilated cardiomyopathy caused by a novel mutation in the lysosome-associated membrane protein-2 (LAMP-2) gene. Patients with pathogenic mutations of this gene typically suffer from Danon disease - a condition that leads to cognitive decline, severe skeletal myopathy, and severe hypertrophic cardiomyopathy. Our patient's presentation and clinical course, however, is different and much less severe than other patients with this disease. He did not suffer from neurologic and musculoskeletal complications. He is also possibly the longest-known survivor of this disease without a heart transplant. This disease is unfamiliar to many physicians, and our case highlights the importance of an awareness of this disorder, particularly because of its implications for both the patient and his family.