Danon Disease

Danon disease, a genetic disorder characterized by heart problems, mental retardation and muscle weakness. Changes in the retina of the eye, leading to visual disturbances, may be present. Males are more severely affected and show symptoms in childhood or early adolescence, while affected females usually develop the symptoms later, in adolescence or adulthood.

The disease is due to a mutation in the gene for LAMP-2 (which stands for lysosome-associated membrane protein 2.), a glycoprotein molecule (a molecule made up of carbohydrate + protein) that is normally located on the membrane surrounding the lysosome (a packet of powerful corrosive enzymes that degrade "garbage" within cells).

Danon disease is named for Dr. M.J. Danon who (together with colleagues) originally described it 1981 as "lysosomal glycogen storage disease with normal acid maltase."

Danon disease usually manifests with the clinical triad of cardiomyopathy, skeletal myopathy, and mental retardation. The skeletal myopathy and mental retardation are less common in females than in males. Regardless of sex, cardiomyopathy can present as a result of symptoms or congestive heart failure (CHF) or an arrhythmia-related event, such as syncope or sudden death. Patients are also newly identified when asymptomatic relatives of patients with established Danon disease are evaluated and are found to have the disease.

Sign and Symptoms:

* Moderate loss of central visual acuity
* Depigmentation of the peripheral retina[8]
* Decreased visual acuity with diffuse choriocapillary atrophy[11]
* Peripheral pigmentary retinopathy
* Lamellar opacities in the lens
* Nonspecific changes on electroretinography

Treatment:

Patients with Danon disease require frequent follow-up, with particular attention to the potential for atrial or ventricular arrhythmias and congestive heart failure (CHF). As is recommended in patients with hypertrophic cardiomyopathy (HCM), a ventricular septal thickness more than 30 mm is considered a risk factor for a life-threatening event, particularly in this group of patients who often have a poor prognosis for survival beyond their teenage years.




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