Danon disease: Description, Causes and Risk Factors:Other names that may be used for this condition are:
Glycogen Storage Disease limited to the heart.
Glycogen Storage Cardiomyopathy.
Glycogen Storage Disease due to LAMP-2 Deficiency.
Glycogen Storage Disease Type IIb.
Lysosomal Glycogen Storage Disease with Normal Acid Maltase Activity.
Lysosomal Glycogen Storage Disease without Acid Maltase Deficiency
X-Linked Vacuolar Cardiomyopathy and Myopathy.
Danon disease is caused by a genetic defect (“mutation”) in a gene called LAMP-2 (Lysosomal-Associated Membrane Protein 2). Danon Disease is a rare lysosomal disorder. Lysosomes are particles found in cells, they contain enzymes that break down substances within the cell. In this disorder there is a defect in the LAMP-2. The role of LAMP-2 is unknown however, it is believed that it plays a role in the day to day development and growth of cells and is important for maintaining a balance between the production of cell structures and their breakdown.Danon disease is a rare genetic disorder characterized by an X-linked dominant inheritance pattern where males are more severely affected than females. Since males have only one X chromosome. Females have two X chromosomes and therefore have an extra X to protect them from disorders of this inheritance nature. Danon Disease also commonly affects males more severely than it does females. Boys often develop symptoms in childhood or in adolescence. Symptoms may not appear in females until adolescence or adulthood. In many males, the disease will progress to the point that death or heart transplantation occurs in the second to third decade of life. Female can also be affected, although usually more mildly and often not until they reach adulthood.The exact frequency of occurrence of Danon Disease is not known. To date not more than 100 cases of Danon Disease have been reported worldwide.Symptoms:Muscle weakness, heart disease, and mental retardation are three main symptoms associated with this disorder. Signs of muscle weakness and heart disease begin to manifest in early childhood or adolescence. Some affected individuals are unable to walk as muscular complications progress. Heart disease associated with Danon Disease involves heart arrhythmias and cardiomyopathy, or severe heart muscle disease. Visual problems may also occur.In females, the symptoms of Danon Disease are less severe and manifest later than they do in affected males. Muscle weakness is present, but commonly less debilitating than it is in males. Heart disease, which may occur, will manifest in adulthood. Symptoms may include visual problems.Diagnosis:Diagnosis is difficult as the condition is unfamiliar to many primary care physicians andspecialists. The diagnosis is suggested on the basis of a family history compatible with X-linkeddominant inheritance and symptoms in affected relatives.Findingglycogen buildup or abnormal vacuoles under the microscope should prompt a considerationof Danon disease.Several mutations have been found on the LAMP-2 gene, and genetic analysis is a necessary diagnostic tool for confirming or disconfirming a diagnosis of Danon Disease. Genetic testing is the best way to get definitive `proof' of the diagnosis of Danon disease.Treatment:There is no specific treatment for this disorder. Treatment is based specifically on any present symptoms and also aims to provide support in the care of the individual. Most treatment is based on heart problems related to this disorder. Genetic counselling may be of benefit to those affected by this disorder and their families.The treatment team for a patient with Danon disease should include a primary care physician and may include several specialists: cardiologist, neurologist, ophthalmologist, geneticist, genetic counselor, rehabilitation physician, educational specialist, physical therapist.The treatment of Danon disease is directed toward the symptoms and problems apparent in each individual. Currently there is no specific therapy that is known to slow the underlying biological problems caused by LAMP-2 protein deficiency. There are no specific Danon disease-directed therapy recommendations at this time. Physical therapy may be helpful in maintaining muscle strength and flexibility. Medications for heart failure should be given when indicated by clinical signs and symptoms. The rapid progression of the cardiomyopathy in some males necessitates prompt considerations for eligibility for heart transplantation. Intellectual disability should be screened for in males and appropriate educational interventions applied as needed. Eye examinations to track the development and progression of retinal disease may be considered. Living relatives at risk for also having Danon disease should be evaluated by a physician. At a minimum, the following should be considered for these relatives: medical history, physical examination (attention to cardiac, neurological, and ocular exams), CPK testing, ECG, and echocardiogram. Genetic consultation and counseling is recommended for all patients and families so that inheritance and reproductive risks are clearly communicated.Disclaimer:The above information is just informative purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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