Emery-Dreifuss muscular dystrophy (EDMD) is characterized by the clinical triad of: joint contractures that begin in early childhood; slowly progressive muscle weakness and wasting initially in a humero-peroneal distribution that later extends to the scapular and pelvic girdle muscles; and cardiac involvement that may manifest as palpitations, presyncope and syncope, poor exercise tolerance, and congestive heart failure along with variable cardiac rhythm disturbances. Age of onset, severity, and progression of muscle and cardiac involvement demonstrate both inter- and intrafamilial variability. Clinical variability ranges from early onset with severe presentation in childhood to late onset with slow progression in adulthood. In general, joint contractures appear during the first two decades, followed by muscle weakness and wasting. Cardiac involvement usually occurs after the second decade and respiratory function may be impaired in some individuals.

Left ventricular noncompaction is a heart (cardiac) muscle disorder that occurs when the lower left chamber of the heart (left ventricle), which helps the heart pump blood, does not develop correctly. Instead of the muscle being smooth and firm, the cardiac muscle in the left ventricle is thick and appears spongy. The abnormal cardiac muscle is weak and has an impaired ability to pump blood because it either cannot completely contract or it cannot completely relax. For the heart to pump blood normally, cardiac muscle must contract and relax fully.\n\nSome individuals with left ventricular noncompaction experience no symptoms at all; others have heart problems that can include sudden cardiac death. Additional signs and symptoms include abnormal blood clots, irregular heart rhythm (arrhythmia), a sensation of fluttering or pounding in the chest (palpitations), extreme fatigue during exercise (exercise intolerance), shortness of breath (dyspnea), fainting (syncope), swelling of the legs (lymphedema), and trouble laying down flat. Some affected individuals have features of other heart defects. Left ventricular noncompaction can be diagnosed at any age, from birth to late adulthood. Approximately two-thirds of individuals with left ventricular noncompaction develop heart failure.

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the SCN5A gene.

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the MYH7 gene.

Any hypertrophic cardiomyopathy in which the cause of the disease is a mutation in the MYL3 gene.

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the CSRP3 gene.

Dilated cardiomyopathy, a disorder characterized by cardiac dilation and reduced systolic function, represents an outcome of a heterogeneous group of inherited and acquired disorders. For background and phenotypic information on dilated cardiomyopathy, see CMD1A (115200).

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the DES gene.

Dilated cardiomyopathy-1G (CMD1G) is an autosomal dominant disorder characterized by ventricular dilatation and systolic contractile dysfunction (Siu et al., 1999). For a general phenotypic description and a discussion of genetic heterogeneity of dilated cardiomyopathy (CMD), see CMD1A (115200).

While most people with familial hypertrophic cardiomyopathy are symptom-free or have only mild symptoms, this condition can have serious consequences. It can cause abnormal heart rhythms (arrhythmias) that may be life threatening. People with familial hypertrophic cardiomyopathy have an increased risk of sudden death, even if they have no other symptoms of the condition. A small number of affected individuals develop potentially fatal heart failure, which may require heart transplantation.\n\nThe symptoms of familial hypertrophic cardiomyopathy are variable, even within the same family. Many affected individuals have no symptoms. Other people with familial hypertrophic cardiomyopathy may experience chest pain; shortness of breath, especially with physical exertion; a sensation of fluttering or pounding in the chest (palpitations); lightheadedness; dizziness; and fainting.\n\nNonfamilial hypertrophic cardiomyopathy tends to be milder. This form typically begins later in life than familial hypertrophic cardiomyopathy, and affected individuals have a lower risk of serious cardiac events and sudden death than people with the familial form.\n\nIn familial hypertrophic cardiomyopathy, cardiac thickening usually occurs in the interventricular septum, which is the muscular wall that separates the lower left chamber of the heart (the left ventricle) from the lower right chamber (the right ventricle). In some people, thickening of the interventricular septum impedes the flow of oxygen-rich blood from the heart, which may lead to an abnormal heart sound during a heartbeat (heart murmur) and other signs and symptoms of the condition. Other affected individuals do not have physical obstruction of blood flow, but the pumping of blood is less efficient, which can also lead to symptoms of the condition. Familial hypertrophic cardiomyopathy often begins in adolescence or young adulthood, although it can develop at any time throughout life.\n\nHypertrophic cardiomyopathy is a heart condition characterized by thickening (hypertrophy) of the heart (cardiac) muscle. When multiple members of a family have the condition, it is known as familial hypertrophic cardiomyopathy. Hypertrophic cardiomyopathy also occurs in people with no family history; these cases are considered nonfamilial hypertrophic cardiomyopathy. 

Hypertrophic cardiomyopathy is a heart condition characterized by thickening (hypertrophy) of the heart (cardiac) muscle. When multiple members of a family have the condition, it is known as familial hypertrophic cardiomyopathy. Hypertrophic cardiomyopathy also occurs in people with no family history; these cases are considered nonfamilial hypertrophic cardiomyopathy. \n\nIn familial hypertrophic cardiomyopathy, cardiac thickening usually occurs in the interventricular septum, which is the muscular wall that separates the lower left chamber of the heart (the left ventricle) from the lower right chamber (the right ventricle). In some people, thickening of the interventricular septum impedes the flow of oxygen-rich blood from the heart, which may lead to an abnormal heart sound during a heartbeat (heart murmur) and other signs and symptoms of the condition. Other affected individuals do not have physical obstruction of blood flow, but the pumping of blood is less efficient, which can also lead to symptoms of the condition. Familial hypertrophic cardiomyopathy often begins in adolescence or young adulthood, although it can develop at any time throughout life.\n\nNonfamilial hypertrophic cardiomyopathy tends to be milder. This form typically begins later in life than familial hypertrophic cardiomyopathy, and affected individuals have a lower risk of serious cardiac events and sudden death than people with the familial form.\n\nThe symptoms of familial hypertrophic cardiomyopathy are variable, even within the same family. Many affected individuals have no symptoms. Other people with familial hypertrophic cardiomyopathy may experience chest pain; shortness of breath, especially with physical exertion; a sensation of fluttering or pounding in the chest (palpitations); lightheadedness; dizziness; and fainting.\n\nWhile most people with familial hypertrophic cardiomyopathy are symptom-free or have only mild symptoms, this condition can have serious consequences. It can cause abnormal heart rhythms (arrhythmias) that may be life threatening. People with familial hypertrophic cardiomyopathy have an increased risk of sudden death, even if they have no other symptoms of the condition. A small number of affected individuals develop potentially fatal heart failure, which may require heart transplantation.

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the FKTN gene.

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the VCL gene.

Atrial fibrillation (AF) is the most common sustained cardiac rhythm disturbance, affecting more than 2 million Americans, with an overall prevalence of 0.89%. The prevalence increases rapidly with age, to 2.3% between the ages of 40 and 60 years, and to 5.9% over the age of 65. The most dreaded complication is thromboembolic stroke (Brugada et al., 1997). For a discussion of genetic heterogeneity of atrial fibrillation, see 608583.

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

Any hypertrophic cardiomyopathy in which the cause of the disease is a mutation in the TNNC1 gene.

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the NEXN gene.

Long QT syndrome (LQTS) is a cardiac electrophysiologic disorder, characterized by QT prolongation and T-wave abnormalities on the EKG that are associated with tachyarrhythmias, typically the ventricular tachycardia torsade de pointes (TdP). TdP is usually self-terminating, thus causing a syncopal event, the most common symptom in individuals with LQTS. Such cardiac events typically occur during exercise and emotional stress, less frequently during sleep, and usually without warning. In some instances, TdP degenerates to ventricular fibrillation and causes aborted cardiac arrest (if the individual is defibrillated) or sudden death. Approximately 50% of untreated individuals with a pathogenic variant in one of the genes associated with LQTS have symptoms, usually one to a few syncopal events. While cardiac events may occur from infancy through middle age, they are most common from the preteen years through the 20s. Some types of LQTS are associated with a phenotype extending beyond cardiac arrhythmia. In addition to the prolonged QT interval, associations include muscle weakness and facial dysmorphism in Andersen-Tawil syndrome (LQTS type 7); hand/foot, facial, and neurodevelopmental features in Timothy syndrome (LQTS type 8); and profound sensorineural hearing loss in Jervell and Lange-Nielson syndrome.

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the SDHA gene.

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the PSEN2 gene.

Any hypertrophic cardiomyopathy in which the cause of the disease is a mutation in the MYOZ2 gene.

Any hypertrophic cardiomyopathy in which the cause of the disease is a mutation in the NEXN gene.

Generalized arterial calcification of infancy (GACI) is characterized by infantile onset of widespread arterial calcification and/or narrowing of large and medium-sized vessels resulting in cardiovascular findings (which can include heart failure, respiratory distress, edema, cyanosis, hypertension, and/or cardiomegaly). Additional findings can include typical skin and retinal manifestations of pseudoxanthoma elasticum (PXE), periarticular calcifications, development of rickets after infancy, cervical spine fusion, and hearing loss. While mortality in infancy is high, survival into the third and fourth decades has occurred.

Atrial fibrillation is the most common sustained cardiac rhythm disturbance, affecting more than 2 million Americans, with an overall prevalence of 0.89%. The prevalence increases rapidly with age, to 2.3% between the ages of 40 and 60 years, and to 5.9% over the age of 65. The most dreaded complication is thromboembolic stroke (Brugada et al., 1997). For a discussion of genetic heterogeneity of familial atrial fibrillation, see ATFB1 (608583).

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the GATAD1 gene.

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the LAMA4 gene.

Deficiency of very long-chain acyl-coenzyme A dehydrogenase (VLCAD), which catalyzes the initial step of mitochondrial beta-oxidation of long-chain fatty acids with a chain length of 14 to 20 carbons, is associated with three phenotypes. The severe early-onset cardiac and multiorgan failure form typically presents in the first months of life with hypertrophic or dilated cardiomyopathy, pericardial effusion, and arrhythmias, as well as hypotonia, hepatomegaly, and intermittent hypoglycemia. The hepatic or hypoketotic hypoglycemic form typically presents during early childhood with hypoketotic hypoglycemia and hepatomegaly, but without cardiomyopathy. The later-onset episodic myopathic form presents with intermittent rhabdomyolysis provoked by exercise, muscle cramps and/or pain, and/or exercise intolerance. Hypoglycemia typically is not present at the time of symptoms.

Any familial isolated dilated cardiomyopathy in which the cause of the disease is a mutation in the RAF1 gene.

Mitochondrial complex IV deficiency nuclear type 13 (MC4DN13) is an autosomal recessive metabolic disorder characterized by the onset of hypertrophic cardiomyopathy soon after birth. Affected individuals have hypotonia, weakness, and failure to thrive, resulting in death in infancy. Laboratory studies show increased serum lactate and decreased levels and activity of mitochondrial respiratory complex IV (summary by Baertling et al., 2015). For a discussion of genetic heterogeneity of mitochondrial complex IV (cytochrome c oxidase) deficiency, see 220110.

COXPD8 is an autosomal recessive disorder due to dysfunction of the mitochondrial respiratory chain. The main clinical manifestation is a lethal infantile hypertrophic cardiomyopathy, but there may also be subtle skeletal muscle and brain involvement. Biochemical studies show combined respiratory chain complex deficiencies in complexes I, III, and IV in cardiac muscle, skeletal muscle, and brain. The liver is not affected (summary by Gotz et al., 2011). For a discussion of genetic heterogeneity of combined oxidative phosphorylation deficiency, see COXPD1 (609060).

CMD2C is characterized by dilated cardiomyopathy of variable severity, with age of onset ranging from 2 to 20 years. Affected individuals exhibit reduction in coenzyme A (CoA) levels. Some severely affected children die in the first few years of life (Iuso et al., 2018). For a general phenotypic description and a discussion of genetic heterogeneity of dilated cardiomyopathy (CMD), see 115200.

Dilated cardiomyopathy-2D (CMD2D) is characterized by neonatal onset of severe cardiomyopathy, with rapid progression to cardiac decompensation and death unless the patient undergoes heart transplantation (Ganapathi et al., 2020). For a general phenotypic description and a discussion of genetic heterogeneity of dilated cardiomyopathy, see 115200.

Familial hypertrophic cardiomyopathy-28 (CMH28) is characterized by asymmetric septal hypertrophy, atrial fibrillation and nonsustained ventricular tachycardia, and risk of sudden death. Dyspnea is the most common symptom, but more than half of affected individuals are asymptomatic. Hypertrabeculation of the left ventricle with noncompaction has been observed in some patients (Ochoa et al., 2018). For a general phenotypic description and discussion of genetic heterogeneity of familial hypertrophic cardiomyopathy, see CMH1 (192600).