This disorder was first described by M.J. Danon and coworkers in 1981. It was originally thought to be a form of glycogen storage disease of which there are multiple types but it has since been shown to be a disease of abnormal metabolism of breakdown products of tissue.
Both males and females are affected but the condition generally has an earlier onset and is more severe in males. Signs and symptoms are highly variable but often have their onset in the second or third decade of life. In some patients the first symptoms are that of visual difficulties such as blurred vision or alterations of color perception. These can progress to legal blindness later in life. In other patients, muscle weakness beginning with the arms and shoulders is the first symptom. In yet others, heart disease with abnormal rhythm, palpitations, and shortness of breath may be the first symptoms of this disorder. Enlargement of the heart and irregular rhythms can be life-threatening.
Some degree of intellectual disability is present in most males but in less than half of females.
This is an X-linked dominant disease in which both sexes are affected. A mutation on the X-chromosome is responsible. Both males and females can pass on the mutation to their children, but since males have only one X-chromosome which they obligatorily transmit to their daughters (their Y-chromosome is passed to their sons), all their daughters and none of their sons will inherit Danon disease. Half of all children of both sexes born to affected mothers will inherit this condition.
The diagnosis is likely made by a cardiologist or a neurologist. However, the eye symptoms may lead to consultation with an ophthalmologist before the systemic symptoms are evident. There is no treatment for the retinal disease in the eye, but if heart symptoms become severe, a heart transplant can be life saving. Rare patients my loss their mobility and become confined to a wheelchair if the muscle weakness becomes severe enough.