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What is Danon disease and explain in detail?
Danon disease (or glycogen storage disease Type IIb) is a metabolic disorder. Danon disease is an X-linked lysosomal and glycogen storage disorder associated with hypertrophic cardiomyopathy, skeletal muscle weakness, and intellectual disability. It is inherited in an X-linked dominant pattern.

Symptoms and signs
Males
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 intellectual disability can be present
Muscle weakness can be severe and can affect endurance and the ability to walk
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.
Cardiac conduction abnormalities can occur. Wolff-Parkinson-White syndrome is a common conduction pattern in Danon disease.
Symptoms are usually gradually progressive
Some individuals may have visual disturbances, and/or retinal pigment abnormalities
Danon Disease is rare and unfamiliar to most physicians. It can be mistaken for other forms of heart disease and/or muscular dystrophies, including Pompe disease.Females
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 intellectual disability are usually absent.
Muscle weakness is often absent or subtle. Some females will tire easily with exercise
Cardiomyopathy is often absent in childhood. Some women will develop this in adulthood. Cardiomyopathy can be associated with atrial fibrillation and embolic strokes.
Cardiac conduction abnormalities can occur. Wolff-Parkinson-White syndrome is a common conduction pattern in Danon disease.
Symptoms in females progress more slowly than in males.
Some females may have visual disturbances, and/or retinal pigment abnormalities
Danon Disease is rare and unfamiliar to most physicians. The milder and more subtle symptoms in females can make it more difficult to diagnose females with Danon Disease

Causes
Although the genetic cause of Danon Disease is known, the mechanism of disease is not well understood. Danon disease involves a genetic defect (mutation) in a gene called LAMP2, which results in a change to the normal protein structure. While the function of the LAMP2 gene is not well understood, it is known that LAMP2 protein is primarily located in small structures within cells called lysosomes.

Genetics
It is associated with LAMP2. The status of this condition as a GSD has been disputed.

Diagnosis
Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a persons medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition