What are the signs and symptoms of Danon disease? Danon disease is characterized by cardiomyopathy. Cardiomyopathy causes the heart muscle to enlarge or become thicker and more rigid than normal. This may make the heart less able to pump blood through the body and can cause serious complications, including sudden death. People with danon disease may also manifest with high levels of serum creatine kinase, eye/vision abnormalities, or Wolff-Parkinson-White syndrome. Wolff-Parkinson-White syndrome is a condition characterized by abnormal electrical pathways in the heart that cause a disruption of the heart's normal rhythm (arrhythmia). Men with Danon disease tend to develop cardiomyopathy prior to the age of 20, and sometimes in early childhood. Women with Danon disease tend to develop cardiomyopathy later in adulthood, however cases of cardiomyopathy in young girls have been reported in the medical literature.  Some women who carry LAMP2 gene mutation never develop any or only very minor symptoms. The following additional signs and symptoms are variably present in people with Danon disease: Learning and development (primarily reported in males, however there has been at least one report of an affected female) Mild intellectual ability Mental retardation Attention deficit disorder Skeletal muscle Exercise intolerance Muscle weakness Eye and vision Peripheral pigmentary retinopathy Lens changes Nearsightedness Abnormal visual fields Signs and symptoms of Danon disease can be very similar to those of hypertrophic cardiomyopathy, even though the underlying disease process differs. You can find detailed information on hypertrophic cardiomyopathy, which includes a brief description of Danon disease, by visiting the following link to GeneReviews. http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=hyper-card The Human Phenotype Ontology provides the following list of signs and symptoms for Danon disease. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Cognitive impairment 90% Gait disturbance 90% Hypertrophic cardiomyopathy 90% Muscle weakness 90% Sudden cardiac death 90% Intellectual disability 70% Arrhythmia - Cardiomegaly - Dilated cardiomyopathy - Elevated serum creatine phosphokinase - EMG: myopathic abnormalities - Exercise intolerance - Exercise-induced muscle cramps - Generalized amyotrophy - Hypokinesia - Myocardial fibrosis - Myocardial necrosis - Pes cavus - Phenotypic variability - Proximal muscle weakness - Visual impairment - Wolff-Parkinson-White syndrome - X-linked dominant inheritance - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.