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Screening among family members of people with known FH is cost-effective. Other strategies such as universal screening at the age of 16 were suggested in 2001. The latter approach may however be less cost-effective in the short term. Screening at an age lower than 16 was thought likely to lead to an unacceptably high rate of false positives.
A 2007 meta-analysis found that "the proposed strategy of screening children and parents for familial hypercholesterolaemia could have considerable impact in preventing the medical consequences of this disorder in two generations simultaneously." "The use of total cholesterol alone may best discriminate between people with and without FH between the ages of 1 to 9 years."
Screening of toddlers has been suggested, and results of a trial on 10,000 one-year-olds were published in 2016. Work was needed to find whether screening was cost-effective, and acceptable to families.
For those at high risk, a combination of lifestyle modification and statins has been shown to decrease mortality.
Genetic contributions are usually due to the additive effects of multiple genes, though occasionally may be due to a single gene defect such as in the case of familial hypercholesterolaemia.
Genetic abnormalities are in some cases completely responsible for hypercholesterolemia, such as in familial hypercholesterolemia, where one or more genetic mutations in the autosomal dominant APOB gene exist, the autosomal recessive "LDLRAP1" gene, autosomal dominant familial hypercholesterolemia ("HCHOLA3") variant of the "PCSK9" gene, or the LDL receptor gene. Familial hypercholesterolemia affects about one in five hundred people.
These unclassified forms are extremely rare:
- Hyperalphalipoproteinemia
- Polygenic hypercholesterolemia
Acquired hyperlipidemias (also called secondary dyslipoproteinemias) often mimic primary forms of hyperlipidemia and can have similar consequences. They may result in increased risk of premature atherosclerosis or, when associated with marked hypertriglyceridemia, may lead to pancreatitis and other complications of the chylomicronemia syndrome. The most common causes of acquired hyperlipidemia are:
- diabetes mellitus
- Use of drugs such as thiazide diuretics, beta blockers, and estrogens
Other conditions leading to acquired hyperlipidemia include:
- Hypothyroidism
- Kidney failure
- Nephrotic syndrome
- Alcohol consumption
- Some rare endocrine disorders and metabolic disorders
Treatment of the underlying condition, when possible, or discontinuation of the offending drugs usually leads to an improvement in the hyperlipidemia.
Another acquired cause of hyperlipidemia, although not always included in this category, is postprandial hyperlipidemia, a normal increase following ingestion of food.
Familial hypercholesterolemia (FH) is a genetic disorder characterized by high cholesterol levels, specifically very high levels of low-density lipoprotein (LDL, "bad cholesterol"), in the blood and early cardiovascular disease. Since individuals with FH underlying body biochemistry is slightly different, their high cholesterol levels are less responsive to the kinds of cholesterol control methods which are usually more effective in people without FH (such as dietary modification and statin tablets). Nevertheless, treatment (including higher statin doses) is usually effective.
FH is classified as a type 2 familial dyslipidemia. There are five types of familial dyslipidemia (not including subtypes), and each are classified from both the altered lipid profile and by the genetic abnormality. For example, high LDL (often due to LDL receptor defect) is type 2. Others include defects in chylomicron metabolism, triglyceride metabolism, and metabolism of other cholesterol-containing particles, such as VLDL and IDL.
About 1 in 300 to 500 people have mutations in the "LDLR" gene that encodes the LDL receptor protein, which normally removes LDL from the circulation, or apolipoprotein B (ApoB), which is the part of LDL that binds with the receptor; mutations in other genes are rare. People who have one abnormal copy (are heterozygous) of the "LDLR" gene may develop cardiovascular disease prematurely at the age of 30 to 40. Having two abnormal copies (being "homozygous") may cause severe cardiovascular disease in childhood. Heterozygous FH is a common genetic disorder, inherited in an autosomal dominant pattern, occurring in 1:500 people in most countries; homozygous FH is much rarer, occurring in 1 in a million births.
Heterozygous FH is normally treated with statins, bile acid sequestrants, or other lipid lowering agents that lower cholesterol levels. New cases are generally offered genetic counseling. Homozygous FH often does not respond to medical therapy and may require other treatments, including LDL apheresis (removal of LDL in a method similar to dialysis) and occasionally liver transplantation.
Both conditions are treated with fibrate drugs, which act on the peroxisome proliferator-activated receptors (PPARs), specifically PPARα, to decrease free fatty acid production. Statin drugs, especially the synthetic statins (atorvastatin and rosuvastatin), can decrease LDL levels by increasing hepatic reuptake of LDL due to increased LDL-receptor expression.
The two forms of this lipid disorder are:
- Familial combined hyperlipidemia (FCH) is the familial occurrence of this disorder, probably caused by decreased LDL receptor and increased ApoB.
- Acquired combined hyperlipidemia is extremely common in patients who suffer from other diseases from the metabolic syndrome ("syndrome X", incorporating diabetes mellitus type II, hypertension, central obesity and CH). Excessive free fatty acid production by various tissues leads to increased VLDL synthesis by the liver. Initially, most VLDL is converted into LDL until this mechanism is saturated, after which VLDL levels elevate.
Renal failure is the major cause of morbidity and mortality in complete LCAT deficiency, while in partial deficiency (fish eye disease) major cause of morbidity is visual impairment due to corneal opacity. These patients have low HDL cholesterol but surprisingly premature atherosclerosis is not seen. However, there are some reported cases.
The disorder affects about 1 out of 1,000,000 people, however epidemiological data are limited and there are regional differences due to cofounder effect (e.g. in Canada) or intermarriage.
Lipoprotein lipase deficiency (also known as "familial chylomicronemia syndrome", "chylomicronemia", "chylomicronemia syndrome" and "hyperlipoproteinemia type Ia") is a rare autosomal recessive lipid disorder caused by a mutation in the gene which codes lipoprotein lipase. As a result, afflicted individuals lack the ability to produce lipoprotein lipase enzymes necessary for effective breakdown of triglycerides.
This condition is caused by a mutation in apolipoprotein E (ApoE), that serves as a ligand for the liver receptors for chylomicrons, IDL and VLDL or Very Low Density lipoprotein receptors. The normal ApoE turns into the defective ApoE2 form due to a genetic mutation. This defect prevents the normal metabolism of chylomicrons, IDL and VLDL, otherwise known as remnants, and therefore leads to accumulation of cholesterol within scavenger cells (macrophages) to enhance development and acceleration of atherosclerosis.
Familial dysbetalipoproteinemia or type III hyperlipoproteinemia (also known as remnant hyperlipidemia, "remnant hyperlipoproteinaemia", "broad beta disease" and "remnant removal disease") is a condition characterized by increased total cholesterol and triglyceride levels, and decreased HDL levels.
Both the familial type and Fish-eye disease are autosomal recessive disorders caused by mutations of the "LCAT" gene located on chromosome 16q22.1, which is the long (q) arm of chromosome 16 a position 22.1. Both diseases are very rare with ~70 reported cases of familial LCAT deficiency and ~30 cases of fish-eye disease.
Apolipoprotein B deficiency (also known as "Familial defective apolipoprotein B-100") is an autosomal dominant disorder resulting from a missense mutation which reduces the affinity of apoB-100 for the low-density lipoprotein receptor (LDL Receptor) . This causes impairments in LDL catabolism, resulting in increased levels of low-density lipoprotein in the blood. The clinical manifestations are similar to diseases produced by mutations of the LDL receptor, such as familial hypercholesterolemia. Treatment may include, niacin or statin or ezetimibe.
It is also known as "normotriglyceridemic hypobetalipoproteinemia".
In at least 25% of cases (the most commonly occurring classification), neurogenic diabetes insipidus is of unknown cause, meaning that the lack of vasopressin production arose from an unknown cause.
It is also due to damage of the hypothalamus, pituitary stalk, posterior pituitary, and can arise from head trauma.
This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. The various types of familial hyperaldosteronism have different genetic causes. Familial hyperaldosteronism type I is caused by the abnormal joining together (fusion) of two similar genes called CYP11B1 and CYP11B2, which are located close together on chromosome 8. These genes provide instructions for making two enzymes that are found in the adrenal glands.
The CYP11B1 gene provides instructions for making an enzyme called 11-beta-hydroxylase. This enzyme helps produce hormones called cortisol and corticosterone. The CYP11B2 gene provides instructions for making another enzyme called aldosterone synthase, which helps produce aldosterone. When CYP11B1 and CYP11B2 are abnormally fused together, too much aldosterone synthase is produced. This overproduction causes the adrenal glands to make excess aldosterone, which leads to the signs and symptoms of familial hyperaldosteronism type I.
Familial hyperaldosteronism type III is caused by mutations in the KCNJ5 gene. The KCNJ5 gene provides instructions for making a protein that functions as a potassium channel, which means that it transports positively charged atoms (ions) of potassium into and out of cells. In the adrenal glands, the flow of ions through potassium channels produced from the KCNJ5 gene is thought to help regulate the production of aldosterone. Mutations in the KCNJ5 gene likely result in the production of potassium channels that are less selective, allowing other ions (predominantly sodium) to pass as well. The abnormal ion flow results in the activation of biochemical processes (pathways) that lead to increased aldosterone production, causing the hypertension associated with familial hyperaldosteronism type III.
The genetic cause of familial hyperaldosteronism type II is unknown.
Familial hyperaldosteronism is a group of inherited conditions in which the adrenal glands, which are small glands located on top of each kidney, produce too much of the hormone aldosterone. Excess aldosterone causes the kidneys to retain more salt than normal, which in turn increases the body's fluid levels and causes high blood pressure. People with familial hyperaldosteronism may develop severe high blood pressure, often early in life. Without treatment, hypertension increases the risk of strokes, heart attacks, and kidney failure. There are other forms of hyperaldosteronism that are not inherited.
Familial hyperaldosteronism is categorized into three types, distinguished by their clinical features and genetic causes. In familial hyperaldosteronism type I, hypertension generally appears in childhood to early adulthood and can range from mild to severe. This type can be treated with steroid medications called glucocorticoids, so it is also known as glucocorticoid-remediable aldosteronism (GRA). In familial hyperaldosteronism type II, hypertension usually appears in early to middle adulthood and does not improve with glucocorticoid treatment. In most individuals with familial hyperaldosteronism type III, the adrenal glands are enlarged up to six times their normal size. These affected individuals have severe hypertension that starts in childhood. The hypertension is difficult to treat and often results in damage to organs such as the heart and kidneys. Rarely, individuals with type III have milder symptoms with treatable hypertension and no adrenal gland enlargement.
This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. The various types of familial hyperaldosteronism have different genetic causes.
It is unclear how common these diseases are. All together they appear to make up less than 1% of cases of hyperaldosteronism.
The lack of vasopressin production usually results from some sort of damage to the pituitary gland. It may be caused due to damage to the brain caused by:
- Benign suprasellar tumors (20% of cases)
- Infections (encephalitis, tuberculosis etc.)
- Trauma (17% of cases) or neurosurgery (9% of cases)
- Non-infectious granuloma (sarcoidosis, Langerhans cell histiocytosis etc.)
- Leukaemia
- Autoimmune - associated with thyroiditis
- Other rare causes which include hemochromatosis and histiocytosis.
Vasopressin is released by the posterior pituitary, but unlike most other pituitary hormones, vasopressin is produced in the hypothalamus. Neurogenic diabetes insipidus can be a failure of production at the hypothalamus, or a failure of release at the pituitary.
Familial dysalbuminemic hyperthyroxinemia is a type of hyperthyroxinemia associated with mutations in the human serum albumin gene.
The term was introduced in 1982.
Familial Isolated Vitamin E Deficiency also known as Ataxia With Vitamin E Deficiency is a rare autosomal recessive neurodegenerative disease. Symptoms are similar to those of Friedreich ataxia.
Familial Isolated Vitamin E Deficiency is caused by mutations in the gene for a-tocopherol transfer protein.
The disease is typically progressive, leading to fulminant liver failure and death in childhood, in the absence of liver transplantation. Hepatocellular carcinoma may develop in PFIC-2 at a very early age; even toddlers have been affected.
Familial dysautonomia is seen almost exclusively in Ashkenazi Jews and is inherited in an autosomal recessive fashion. Both parents must be carriers in order for a child to be affected. The carrier frequency in Jewish individuals of Eastern European (Ashkenazi) ancestry is about 1/30, while the carrier frequency in non-Jewish individuals is unknown. If both parents are carriers, there is a one in four, or 25%, chance with each pregnancy for an affected child. Genetic counseling and genetic testing is recommended for families who may be carriers of familial dysautonomia.
Worldwide, there have been approximately 600 diagnoses recorded since discovery of the disease, with approximately 350 of them still living.
Although not based on a human clinical trial, the only currently accepted disease-modifying therapeutic strategy available for familial amyloid cardiomyopathy is a combined liver and heart transplant. Treatments aimed at symptom relief are available, and include diuretics, pacemakers, and arrhythmia management. Thus, Senile systemic amyloidosis and familial amyloid polyneuropathy are often treatable diseases that are misdiagnosed.
In 2013, the European Medicines Agency approved the drug tafamidis (Vyndaqel) to slow the progression of familial amyloid polyneuropathy, a related disease caused by TTR aggregation that first presents as an autonomic and/or peripheral neuropathy (later progressing to a cardiomyopathy).