Danon Disease: Clinical Manifestations, Pathophysiology, and Treatment

Danon disease is an X-linked dominant vacuolar disease caused by a mutation in lysosome-associated membrane protein-2 (LAMP-2). LAMP-2 has 3 known subtypes, with LAMP-2B being the most important in Danon disease. It plays a role in macroautophagy and is one of the reasons why those with Danon disease have issues degrading cytoplasmic components. Autophagic vacuoles with unique sacrolemmal features are a characteristic finding in Danon disease. This condition is rare but causes fatal cardiomyopathy in those it affects. It is known to cause a triad of intellectual disability, cardiomyopathy, and skeletal myopathy in males, but is mostly restricted to cardiomyopathy in females. The cardiomyopathy is most often hypertrophic cardiomyopathy, but can also be dilated cardiomyopathy, especially in females. Both ventricular and atrial arrhythmias are common in those with Danon disease. They commonly have slurring of the upstroke of the QRS complex, or ventricular depolarization, on electrocardiogram and extensive late gadolinium uptake with mid-interventricular septal sparing on cardiac magnetic resonance imaging. Treatment currently consists of heart transplant, and gene therapy studies are in phase II clinical trials using RP-A501, a recombinant adeno-associated virus-9 containing the transgene LAMP-2, to deliver LAMP-2 to cardiomyocytes.