無β脂蛋白血症

Abetalipoproteinemia is a rare autosomal recessive disorder marked by low or absent levels of plasma cholesterol, low-density lipoproteins, and very-low-density lipoproteins. It should not be confused with a deficiency in beta-lipoproteins. Hallmark symptoms include fat malabsorption, spinocerebellar degeneration, acanthocytosis, and retinitis pigmentosa. This activity reviews the etiology, epidemiology, pathophysiology, evaluation, and treatment considerations of this disease and highlights the role of the collaboration between interprofessional team members. Explain how abetalipoproteinemia manifests in each of the three main organ systems that it affects. Review the importance of collaboration between interprofessional team members for improved recognition and treatment of abetalipoproteinemia. Abetalipoproteinemia (ABL) is a rare autosomal recessive disorder marked by low or absent levels of plasma cholesterol, low-density lipoproteins (LDLs), and very-low-density lipoproteins (VLDLs). It should not be confused with a deficiency in beta-lipoproteins. Hallmark symptoms include fat malabsorption, spinocerebellar degeneration, acanthocyte red blood cells, and retinitis pigmentosa. [[1]]( [[2]]( Abetalipoproteinemia is caused by a homozygous autosomal recessive mutation in the MTTP gene. More than 33 mutations that cause the disease have been identified. The gene codes for microsomal triglyceride protein (MTP) that mediates intracellular chylomicron or VLDL assembly and transport in the intestinal mucosa and hepatocytes. Most of the signs and symptoms of the disease result from a severe deficiency of fats and fat-soluble vitamins, especially vitamin E. It usually presents in infants as failure to thrive, steatorrhea, and abdominal distension and results in spinocerebellar degeneration and retinitis pigmentosa.[[3]]( Beta apolipoproteins are very large apolipoproteins. They are critically important for the secretion and formation of chylomicrons (CMs) and VLDL. Abnormalities that impede this process result in abetalipoproteinemia and hypobetalipoproteinemia. [[6]]( [[7]]( [[8]]( MTP acts as a chaperone that facilitates the transfer of lipids onto apo B. MTP is found within the lumen of microsomes in the liver and intestinal mucosa and catalyzes the transfer of triglyceride, cholesteryl esters, and phosphatidylcholine between membranes. Lipid transport rates decrease in the order of triglyceride to cholesteryl ester to diglyceride to cholesterol to phosphatidylcholine. Unlike other lipid transfer proteins, MTP is a heterodimer containing subunits of molecular mass 58 and 97 kDa. The large 97-kDa subunit possesses the lipid transfer activity or confers lipid transfer activity on the complex. The large subunit of MTP may be missing in abetalipoproteinemia. Initial assembly occurs in the endoplasmic reticulum, where apolipoproteins, cholesterol, phospholipid, and triacylglycerides are synthesized and incorporated into lipoprotein particles. The particles are subsequently transported to Golgi and secreted. Each lipoprotein is specific in its lipid composition and the type of apolipoproteins it possesses. The two beta apolipoproteins are B-100 and B-48. ApoB-100 is carried on VLDL. ApoB-100, synthesized by the liver, is larger than apoB-48, which is made up of 4536 amino acids. Unlike apoB-48, apoB-100 contains the binding site essential for LDL uptake by hepatocyte LDL receptors. ApoB-48 is carried on CMs and is derived from the same gene as apoB-100.[[1]]( These manifestations include diarrhea and fat-soluble vitamin deficiency. They are evident from infancy. Diarrhea may not be a prominent symptom later, though, because patients learn to avoid fatty foods. However, the deficits in fat-soluble vitamins continue because their assimilation and transport depend heavily on the integrity of the apoB pathway. It is worth noting that high-dose vitamin E supplementation only results in marginally increased serum vitamin levels. In