The first description of Danon Disease was in 1981 when 2 boys with heart and skeletal muscle disease (muscle weakness) and mental retardation were described. The disease is named after Dr. Danon who first wrote about the disease.
Danon Disease looked initially like another rare genetic condition called 'Pompe' disease. Under the microscope, muscles from the Danon Disease patients looked similar to muscles from Pompe disease patients. However the tests for Pompe disease are normal in Danon Disease patients. This shows that Danon Disease is caused by something different than Pompe disease.
In males the symptoms of Danon Disease are more severe. Features of Danon Disease in males are:
An early age of onset of muscle weakness and heart disease (onset in childhood or adolescence)
Some learning problems or mental retardation can be present
The muscle weakness can be severe and can affect endurance and even the ability to walk
The heart disease (cardiomyopathy) can be severe and can lead to a need for medications. It usually progress to heart failure, commonly complicated by atrial fibrillation and embolic strokes with severe neurological disability, leading to death unless heart transplant is performed.
The symptoms are usually progressive and the boys tend to gradually get worse
Some boys may have problems with their vision or a problem with the pigment in their retinas (in the back of their eyes)
Danon Disease is rare and unfamiliar to most physicians. It can be mistaken for other forms of heart disease and/or muscular dystrophies.
In females the symptoms of Danon Disease are less severe. Common symptoms of Danon Disease in females are:
A later age of onset of symptoms. Many females will not have obvious symptoms until late adolescence or even adulthood.
Learning problems and mental retardation are usually ABSENT
Muscle weakness is often absent or subtle. Some females will tire easily with exercise
Heart muscle disease (cardiomyopathy) is often absent in girls: some women will develop this in adulthood. Cardiomyopathy can be associated with atrial fibrillation and embolic strokes.
Problems with the electrical conduction in the heart can occur. Sometimes the conduction problem is called 'Wolff-Parkinson-White' syndrome
Symptoms in females progress more slowly than in males. Heart disease may not be a problem for females until adulthood
Some females will have problems with their vision or a problem with the pigment in the back of their retinas (in the back of their eyes)
Danon Disease is rare and unfamiliar to most physicians. The milder and more subtle symptoms in females probably make it harder to diagnose females who have Danon Disease
Causes of Danon Disease
The cause of Danon Disease is known, but not well-understood. The genetic defect involves a gene called LAMP2. In persons with Danon Disease the LAMP2 gene is damaged (or 'mutated') and normal LAMP2 protein is no longer made. While we do not fully understand what the function of the LAMP2 gene is, we do know that LAMP2 protein is located in small structures in our cells called lysosomes