A Rare Cause of Cardiac Hypertrophy: Danon Disease

Cardiac hypertrophy is a common clinical finding and may appear as a cardiac manifestation of numerous diseases. In addition to frequently encountered causes such as hypertension and valvular heart disease, clinicians must also consider cardiac amyloidosis, hypertrophic cardiomyopathies, and various rare genetic conditions. Danon disease is a rare X-linked dominant multisystem disorder characterized by cardiomyopathy, skeletal myopathy, and intellectual disability. It results from defects in the lysosome-associated membrane protein-2 (LAMP2) gene, and numerous pathogenic mutations have been described. Here, we present the case of a 64-year-old woman who was evaluated for suspected cardiac amyloidosis due to marked left ventricular hypertrophy and was subsequently diagnosed with Danon disease. The coexistence of Danon disease and cardiac amyloidosis is exceedingly uncommon and highlights the importance of considering rare etiologies in patients presenting with hypertrophic phenotypes.