Analbuminemia: A Rare Genetic Disorder of Albumin Synthesis

Analbuminemia: A Rare Genetic Disorder of Albumin Synthesis

Analbuminemia is a rare autosomal recessive disorder that affects the synthesis of albumin, the most abundant protein in human blood plasma. Albumin plays a vital role in maintaining the osmotic pressure, transporting various substances, and regulating the fluid balance in the body. People with analbuminemia have very low levels of circulating serum albumin, usually less than 1 g/L, compared to the normal range of 35-50 g/L .

Despite the importance of albumin, analbuminemia is a benign condition that does not cause any major health problems. Most affected individuals have few or mild symptoms, such as edema (swelling), hypotension (low blood pressure), fatigue, and sometimes lower body lipodystrophy (abnormal fat distribution) in adult females . The lack of albumin is compensated by increased amounts of other plasma proteins, such as immunoglobulins, transferrin, and alpha-1 antitrypsin. However, analbuminemia may increase the risk of fetal or neonatal death in siblings of affected individuals, which may explain the rarity of the disorder.

Analbuminemia is caused by mutations in the ALB gene, which encodes the albumin protein. The ALB gene is located on chromosome 4 and contains 15 exons. So far, more than 20 different mutations have been identified in analbuminemic patients, most of them affecting the splicing or stability of the ALB mRNA . The mutations result in a complete or near-complete absence of albumin production in the liver.

Analbuminemia is diagnosed by measuring the serum albumin concentration using biochemical methods, such as electrophoresis or immunonephelometry. Genetic testing can confirm the diagnosis by detecting the specific mutation in the ALB gene. Analbuminemia is inherited in an autosomal recessive manner, which means that both copies of the ALB gene must be mutated for a person to be affected. Parents of an affected child are usually asymptomatic carriers who have one mutated and one normal copy of the ALB gene.

There is no specific treatment for analbuminemia, as it does not cause any serious complications. Affected individuals may benefit from a high-protein diet and salt restriction to reduce edema and hypotension. Albumin infusion may be considered in some cases, such as surgery, trauma, or severe infection, to improve the blood volume and pressure . However, albumin infusion may also cause adverse reactions, such as allergic reactions or fluid overload. Therefore, it should be used with caution and under medical supervision.

Analbuminemia is a rare genetic disorder that affects the synthesis of albumin, a key protein in human blood plasma. It causes very low levels of serum albumin, but does not lead to any major health problems. It is diagnosed by biochemical and genetic tests and managed by supportive measures.

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Analbuminemia and Lipid Metabolism

One of the most striking features of analbuminemia is the abnormal lipid profile of affected individuals. They have significantly elevated levels of total and LDL cholesterol, but normal or low levels of HDL cholesterol and triglycerides . The mechanism behind this hypercholesterolemia is not fully understood, but it may involve several factors, such as increased synthesis, decreased catabolism, or altered transport of cholesterol and lipoproteins in the absence of albumin.

Although high levels of LDL cholesterol are usually associated with an increased risk of atherosclerosis and cardiovascular disease, analbuminemic patients do not seem to develop these complications. This may be due to the protective effect of other plasma proteins, such as immunoglobulins, that bind to LDL and prevent its oxidation and uptake by macrophages. Moreover, analbuminemic patients have normal levels of apolipoprotein B (apoB), the main protein component of LDL, which may also reduce the atherogenic potential of LDL.

Another interesting aspect of analbuminemia is the lower body lipodystrophy that occurs in some adult females. This condition is characterized by a loss of subcutaneous fat in the legs and buttocks, resulting in a thin and muscular appearance. The cause of this lipodystrophy is unknown, but it may be related to hormonal factors, such as estrogen or insulin, that modulate the distribution and metabolism of fat tissue. The lipodystrophy does not affect the health or quality of life of affected individuals.

Analbuminemia and Albumin Replacement Therapy

Analbuminemia and Lipid Metabolism

Albumin replacement therapy is the administration of exogenous albumin to increase the serum albumin concentration and improve the fluid balance and hemodynamics in patients with hypoalbuminemia. Albumin replacement therapy is commonly used in various clinical settings, such as liver cirrhosis, nephrotic syndrome, burns, sepsis, and surgery. However, its efficacy and safety are still controversial, as some studies have shown no benefit or even harm from albumin infusion. Therefore, albumin replacement therapy should be used with caution and according to the guidelines and recommendations of professional societies.

Analbuminemic patients may require albumin replacement therapy in some situations where they are at risk of hypovolemia (low blood volume) or hypotension (low blood pressure), such as surgery, trauma, or severe infection . Albumin infusion may help to restore the blood volume and pressure and prevent organ damage. However, albumin replacement therapy may also have some drawbacks for analbuminemic patients, such as:

  • Allergic reactions: Some patients may develop hypersensitivity reactions to exogenous albumin, such as rash, itching, fever, or anaphylaxis. These reactions may be more common in analbuminemic patients who have no or very low levels of endogenous albumin and may develop antibodies against it.
  • Fluid overload: Albumin infusion may cause excessive fluid retention in the interstitial space (the space between cells), leading to edema (swelling), pulmonary edema (fluid accumulation in the lungs), or heart failure. This may be more likely in analbuminemic patients who have impaired renal function or cardiac function.
  • Hypercoagulability: Albumin infusion may increase the blood viscosity (thickness) and the risk of thrombosis (blood clot formation) in analbuminemic patients who have high levels of other plasma proteins that promote coagulation (clotting), such as fibrinogen or immunoglobulins.

Therefore, albumin replacement therapy should be used with caution and under medical supervision in analbuminemic patients. The dose and duration of albumin infusion should be adjusted according to the clinical condition and response of each patient. The serum albumin concentration should be monitored regularly during and after albumin infusion to avoid overcorrection or undercorrection. The potential benefits and risks of albumin replacement therapy should be weighed carefully for each patient.

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