Hypolipidemia

Hypolipidemia is a decrease in lipoproteins in the blood plasma caused by primary (genetic) or secondary factors. This condition is usually asymptomatic and is diagnosed accidentally during a screening study of lipid levels.

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Causes hypolipidemia

Hypolipidemia is diagnosed when the total cholesterol level:

• < 120 mg/dL (< 3.1 mmol/L) or LDL
• < 50 mg/dL (< 0.13 mmol/L).

Secondary causes of hypolipidemia are much more common than primary causes and include hyperthyroidism, chronic infections and other infectious and inflammatory diseases, hematologic and other malignancies, malnutrition (including that associated with chronic alcohol use), and gastrointestinal malabsorption. When an unexpected laboratory finding of low cholesterol or LDL is detected in a patient not taking lipid-lowering drugs, diagnostic testing should be immediately performed, including determination of AST, ALT, and TSH; a negative result of additional testing speaks in favor of possible primary causes that can cause such a condition as hypolipidemia.

There are three main disorders, known as primary causes of hypolipidemia, in which single or multiple genetic mutations lead to overproduction or impaired clearance of LDL.

Abetalipoproteinemia (Bazin-Kornzweig syndrome) is an autosomal recessive inherited disorder caused by a mutation in the gene for microsomal triglyceride transfer protein, a special protein required for the formation of chylomicrons and VLDL. Dietary fats cannot be absorbed, and both lipoprotein metabolic pathways are virtually absent in the serum. Total cholesterol is usually < 45 mg/dL (1.16 mmol/L), TG < 20 mg/dL (< 0.23 mmol/L), and LDL is undetectable. This condition is often first diagnosed in newborns with fat malabsorption syndrome, steatorrhea, and growth and developmental delays. Mental retardation may result. Because vitamin E is distributed to peripheral tissues via VLDL and LDL, most patients eventually develop severe vitamin E deficiency. Clinical symptoms and signs include visual changes resulting from gradual retinal degeneration, development of sensory neuropathy, posterior funicular white matter lesions, and cerebellar symptoms (incoordination, ataxia, and muscle hypertonicity), which eventually lead to death. Red blood cell acanthocytosis is a characteristic microscopic finding. Hypolipidemia is diagnosed by the absence of apo B in plasma; small intestinal biopsy reveals the absence of microsomal transfer protein. Treatment of this hypolipidemia involves high doses (100-300 mg/kg once daily) of vitamin E in combination with dietary fats and other fat-soluble vitamins.

Hypobetalipoproteinemia is an autosomal dominant inherited pathology caused by mutations in the gene encoding apo B. Heterozygous patients have a shortened apo B, which leads to accelerated LDL clearance. At the manifestation of pathology, no clinical symptoms are detected, except for the level of total cholesterol < 120 mg / dl and LDL < 80 mg / dl. The triglyceride level is normal. Homozygous patients have a shorter truncation of apo B, leading to a more pronounced decrease in lipid levels (total cholesterol < 80 mg / dl, LDL < 20 mg / dl) or complete cessation of apo B synthesis, leading to the development of symptoms of abetalipoproteinemia. Hypolipidemia is established on the basis of detectable low levels of LDL and apo B; Hypobetalipoproteinemia and abetalipoproteinemia are characteristic conditions that are inherited over many generations. Hetero- and homozygous patients with low but detectable LDL-C do not require any therapy. This hypolipidemia is treated in homozygous patients with undetectable LDL-C levels in the same way as abetalipoproteinemia.

Chylomicron retention disease is an autosomal recessive condition caused by an unknown mutation that results in deficiency of apo B secretion from enterocytes. Chylomicron synthesis is absent, but VLDL synthesis remains intact. Affected infants have fat malabsorption syndrome, steatorrhea, and growth retardation, which may lead to neurologic symptoms similar to those seen in abetalipoproteinemia. Hypolipidemia is diagnosed by small intestinal biopsy in patients with low plasma cholesterol and no postprandial chylomicrons. Treatment involves diet therapy (foods rich in fats and fat-soluble vitamins).

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Treatment hypolipidemia

Secondary hypolipidemia is treated by eliminating the underlying cause. Primary hypolipidemia often does not require treatment, but patients with certain genetic abnormalities require high doses of vitamin E.