MedGen

Hypertrophic cardiomyopathy (HCM) is typically defined by the presence of unexplained left ventricular hypertrophy (LVH). Such LVH occurs in a non-dilated ventricle in the absence of other cardiac or systemic disease capable of producing the observed magnitude of increased LV wall thickness, such as pressure overload (e.g., long-standing hypertension, aortic stenosis) or storage/infiltrative disorders (e.g., Fabry disease, amyloidosis). The clinical manifestations of HCM range from asymptomatic LVH to progressive heart failure to sudden cardiac death (SCD), and vary from individual to individual even within the same family. Common symptoms include shortness of breath (particularly with exertion), chest pain, palpitations, orthostasis, presyncope, and syncope. Most often the LVH of HCM becomes apparent during adolescence or young adulthood, although it may also develop late in life, in infancy, or in childhood. [from NCBI]

Sick sinus syndrome may be encountered at any age but is primarily a disease of the elderly and is often secondary to other cardiac disorders when diagnosed in younger individuals. Symptoms are often intermittent and/or nonspecific and include dizziness, syncope, and heart failure. The only effective treatment for symptomatic and irreversible sinus node dysfunction is permanent cardiac pacing, and sick sinus syndrome remains the most common indication for permanent pacemaker implantation (summary by Holm et al., 2011). For a general phenotypic description and a discussion of genetic heterogeneity of sick sinus syndrome, see SSS1 (608567). [from OMIM]

Any atrial heart septal defect in which the cause of the disease is a mutation in the MYH6 gene. [from MONDO]

An autosomal dominant subtype of familial hypertrophic cardiomyopathy caused by mutation(s) in the MYH6 gene, encoding myosin-6. [from NCI]

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the MYH6 gene. [from MONDO]

Familial dilated cardiomyopathy is a genetic form of heart disease. It occurs when heart (cardiac) muscle becomes thin and weakened in at least one chamber of the heart, causing the open area of the chamber to become enlarged (dilated). As a result, the heart is unable to pump blood as efficiently as usual. To compensate, the heart attempts to increase the amount of blood being pumped through the heart, leading to further thinning and weakening of the cardiac muscle. Over time, this condition results in heart failure.

It usually takes many years for symptoms of familial dilated cardiomyopathy to cause health problems. They typically begin in mid-adulthood, but can occur at any time from infancy to late adulthood. Signs and symptoms of familial dilated cardiomyopathy can include an irregular heartbeat (arrhythmia), shortness of breath (dyspnea), extreme tiredness (fatigue), fainting episodes (syncope), and swelling of the legs and feet. In some cases, the first sign of the disorder is sudden cardiac death. The severity of the condition varies among affected individuals, even in members of the same family. [from MedlinePlus Genetics]