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Deep Learning Technology: Sebastian Arnold, Betty van Aken, Paul Grundmann, Felix A. Gers and Alexander Löser. Learning Contextualized Document Representations for Healthcare Answer Retrieval. The Web Conference 2020 (WWW'20)
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Individuals experiencing episodic bleeding as a result of congenital dysfibrinogenemia should be treated at a center specialized in treating hemophilia. They should avoid all medications that interfere with normal platelet function. During bleeding episodes, treatment with fibrinogen concentrates or in emergencies or when these concentrates are unavailable, infusions of fresh frozen plasma and/or cryoprecipitate (a fibrinogen-rich plasma fraction) to maintain fibrinogen activity levels >1 gram/liter. Tranexamic acid or fibrinogen concentrates are recommended for prophylactic treatment prior to minor surgery while fibrinogen concentrates are recommended prior to major surgery with fibrinogen concentrates usage seeking to maintain fibrinogen activity levels at >1 gram/liter. Women undergoing vaginal or Cesarean child birth should be treated at a hemophilia center with fibrinogen concentrates to maintain fibrinogen activity levels at 1.5 gram/liter. The latter individuals require careful observation for bleeding during their post-partum periods.
Individuals experiencing episodic thrombosis as a result of congenital dysfibrinogenemia should also be treated at a center specialized in treating hemophilia using antithrombotic agents. They should be instructed on antithrombotic behavioral methods fur use in high risk situations such as long car rides and air flights. Venous thrombosis should be treated with low molecular weight heparin for a period that depends on personal and family history of thrombosis events. Prophylactic treatment prior to minor surgery should avoid fibrinogen supplementation and use prophylactic anticoagulation measures; prior to major surgery, fibrinogen supplementation should be used only if serious bleeding occurs; otherwise, prophylactic anticoagulation measures are recommended.
Treatment of asymptomatic congenital dysfibrinogenemia depends in part on the expectations of developing bleeding and/or thrombotic complications as estimated based on the history of family members with the disorder and, where available, determination of the exact mutation causing the disorder plus the propensity of the particular mutation type to develop these complications. In general, individuals with this disorder require regular follow-up and multidiscipline management prior to surgery, pregnancy, and giving childbirth. Women with the disorder appear to have an increased rate of miscarriages and all individuals with fibrinogen activity in clotting tests below 0.5 grams/liter are prone to bleeding and spontaneous abortions. Women with multiple miscarriages and individuals with excessively low fibrinogen activity levels should be considered for prophylaxis therapy with fibrinogen replacement during pregnancy, delivery, and/or surgery.
All individuals with mutations causing fibrinogen storage disease have low blood fibrinogen levels but usually lack severe bleeding episodes, thrombotic episodes or liver disease. Individuals that do have fibrinogen storage disease often come to attention either because they have close relatives with the disease, are found to be hypofibrinogenmic during routing testing, or exhibit clinical (e.g. jaundice) or laboratory (e.g. elevated blood levels of liver enzymes) evidence of liver disease. Unlike other forms of congenital hypofibrinogenemia, a relatively high percentage of individuals with fibrinogen storage disease have been diagnosed in children of very young age.
Congenital hypofibrinogenemia is a rare disorder in which one of the two genes responsible for producing fibrinogen, a critical blood clotting factor, is unable to make a functional fibrinogen glycoprotein because of an inherited mutation. In consequence, liver cells, the normal site of fibrinogen production, make small amounts of this critical coagulation protein, blood levels of fibrinogen are low, and individuals with the disorder may suffer a coagulopathy, i.e. a diathesis or propensity to experience episodes of abnormal bleeding. However, individuals with congenital hypofibringenemia may also suffer episodes of abnormal blood clot formation, i.e. thrombosis. This seemingly paradoxical propensity to develop thrombosis in a disorder causing a decrease in a critical protein for blood clotting may be due to the function of fibrin (the split product of fibrinogen that is the basis for forming blood clots) to promote the lysis or desolution of blood clots. Lower levels of fibrin may reduce the lysis of early fibrin strand depositions and thereby allow these depositions to develop into clots.
Congenital hypofibrinogenemia must be distinguished from: a) congenital afibrinogenemia, a rare disorder in which blood fibrinogen levels are either exceedingly low or undetectable due to mutations in both fibrinogen genes; b) congenital hypodysfibrinogenemia, a rare disorder in which one or more genetic mutations cause low levels of blood fibrinogen, at least some of which is dysfunctional and thereby contributes to excessive bleeding; and c) acquired hypofibrinogenemia, a non-hereditary disorder in which blood fibrinogen levels are low because of e.g. severe liver disease or because of excessive fibrinogen consumption resulting from, e.g. disseminated intravascular coagulation.
Certain gene mutations causing congenital hypfibrinogenemia disrupt the ability of liver cells to secrete fibrinogen. In these instances, the un-mutated gene maintains blood fibrinogen at reduce levels but the mutated gene produces a fibrinogen that accumulates in liver cells sometimes to such extents that it becomes toxic. In the latter cases, liver disease may ensue in a syndrome termed fibrinogen storage disease.
Blood relatives of the proband case should be evaluated for the presence of hypodysfibrinogenemia. Individuals with the disorder need to be advised on its inheritance, complications, and preventative measures that can be taken to avoid bleeding and/or thrombosis. Since >80% of individuals may develop bleeding or thrombosis complications of the disorder, asymptomatic individuals diagnosed with hydposyfibrinogenemia are best handled at a specialized center in order to benefit from multidisciplinary management.
Measures to prevent and/or treat complications of hypodysfibrinogenemia should be tailored to the personal and family history of the individual by a specialized center. Individuals with a personal or family history of bleeding are considered to be of low risk of bleeding when their functional fibrinogen levels are >1 gram/liter for major surgery, >0.5 gram/liter for minor surgery, >0.5 to 1-2 gram/liter for spontaneous bleeding (depending on its severity), >0.5 to > 1 gram/liter for the first two trimesters of pregnancy, and >1 to <2 gram/liter for the last trimester of pregnancy and postpartum period. Functional fibrinogen below these levels should be treated preferably with fibrinogen concentrate or if not available, fibrinogen-rich cryoprecipitate or plasma to attain low risk levels of functional fibrinogen. Antifibrinolytic drugs such as tranexamic acid or (ε-aminocaproic acid) may be considered as an alternative preventative or therapeutic treatments in cases of minor surgery, dental extractions, mucosal bleeding, or other episodes of mild bleeding. In individuals with a personal or family history of thrombosis, should be considered for long-term anticoagulation drugs such as low molecular weight heparin, coumadin, or rivaroxaban.
Fibrinogen disorders are set of hereditary or acquired abnormalities in the quantity and/or quality of circulating fibrinogens. The disorders may lead to pathological bleeding and/or blood clotting or the deposition of fibrinogen in the liver, kidneys, or other organs and tissues. These disorders include:
- Congenital afibrinogenemia, an inherited blood disorder in which blood does not clot normally due to the lack of fibrinogen; the disorder causes abnormal bleeding and thrombosis.
- Congenital hypofibrinogenemia, an inherited disorder in which blood may not clot normally due to reduced levels of fibrinogen; the disorder may cause abnormal bleeding and thrombosis.
- Fibringogen storage disease, a form of congenital hypofibrinogenemia in which specific hereditary mutations in fibrinogen cause it to accumulate in, and damage, liver cells. The disorder may lead to abnormal bleeding and thrombosis but also to cirrhosis.
- Congenital dysfibrinogenemia, an inherited disorder in which normal levels of fibrinogen composed at least in part of a dysfunctional fibrinogen may cause abnormal bleeding and thrombosis.
- Hereditary fibrinogen Aα-Chain amyloidosis, a form of dysfibrinogenemia in which certain fibrinogen mutations cause blood fibrinogen to accumulate in the kidney and cause one type of familial renal amyloidosis; the disorder is not associated with abnormal bleeding or thrombosis.
- Acquired dysfibrinogenemia, a disorder in which normal levels of fibrinogen are composed at least in part of a dysfunctional fibrinogen due to an acquired disorder (e.g. liver disease) that leads to the synthesis of an incorrectly glycosylated (i.e. wrong amount of sugar residues) added to an otherwise normal fibrinogen. The incorrectly glycosalated fibrinogen is dysfunctional and may cause pathological episodes of bleeding and/or blood clotting.
- Congenital hypodysfibrinogenemia, an inherited disorder in which low levels of fibrinogen composed at least in part of a dysfunctional fibrinogen may cause pathological episodes of bleeding or blood clotting.
- Cryofibrinogenemia, an acquired disorder in which fibrinogen precipitates at cold temperatures and may lead to the intravascular precipitation of fibrinogen, fibrin, and other circulating proteins thereby causing the infarction of various tissues and bodily extremities.
Circulating fibrinogen is a glycoprotein made of two trimers each of which is composed of three polypeptide chains, Aα (also termed α) encoded by the "FGA" gene, Bβ (also termed β) encoded by the "FGB" gene, and γ encoded by the "FGG" gene. All three genes are located on the long or "p" arm of human chromosome 4 (at positions 4q31.3, 4q31.3, and 4q32.1, respectively) and are the sites where mutations occur that code for a dysfunctional fibrinogen and/or reduced fibrinogen levels which are the cause of congenital hypodysfibrinogenemia.
The occurrence of cryofibrinogenemia as defined by a 4 °C-induced formation of fibrinogen-based precipitation in plasma occurs in 2% to 9% of asymptomatic individuals and 8% to 13% of hospitalized patients without symptoms attributable to this precipitation. Most of these cases have relatively low levels of cold temperature-induced fibrinogen precipitate levels (<50 milligram/liter of fibrinogen) and do not have a disorder associated with the development of cryofibrinogenmia.
Cryoglobulonemia may occur without evidence of an underlying associated disorders, i.e. primary cryoglobulinemia (also termed essential cryoglobulinemia) or, far more commonly, with evidence of an underlying disease, i.e. secondary cryoglobulonemia. Secondary cryofibrinoenemia can develop in individuals suffering infection (~12% of cases), malignant or premalignant disorders (21%), vasculitis (25%), and autoimmune diseases (42%). In these cases of the secondary disorder, cryofibinogenema may or may not cause tissue injury and/or other symptoms and the actual cause-effect relationship between these diseases and the development of cryofibrinogenmia is unclear. Cryofibrinogenemia can also occur in association with the intake of certain drugs.
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.
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".
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.
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 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 prognosis is guarded with an overall mortality of 50%. Poor prognostic factors included HLH associated with malignancy, with half the patients dying by 1.4 months compared to 22.8 months for non-tumour associated HLH patients.
Secondary HLH in some individuals may be self-limited because patients are able to fully recover after having received only supportive medical treatment (i.e., IV immunoglobulin only). However, long-term remission without the use of cytotoxic and immune-suppressive therapies is unlikely in the majority of adults with HLH and in those with involvement of the central nervous system (brain and/or spinal cord).
Currently, there is no specific treatment to correct the LCAT deficiency so therapy is focused on symptom relief. Corneal transplant may be considered for patients presenting with severely impaired vision caused by cholesterol corneal opacities. Dialysis may be required for patients presenting with renal failure, and kidney transplant may be considered.
Testing the general population under the age of 40 without symptoms is of unclear benefit.
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.
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.
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.
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.
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.
Diet has an effect on blood cholesterol, but the size of this effect varies between individuals. Moreover, when dietary cholesterol intake goes down, production (principally by the liver) typically increases, so that blood cholesterol changes can be modest or even elevated. This compensatory response may explain hypercholesterolemia in anorexia. A 2016 review found tentative evidence that dietary cholesterol is associated with higher blood cholesterol. Trans fats have been shown to reduce levels of HDL while increasing levels of LDL. LDL and total cholesterol also increases by very high fructose intake.
Familial dysalbuminemic hyperthyroxinemia is a type of hyperthyroxinemia associated with mutations in the human serum albumin gene.
The term was introduced in 1982.