Mechanisms of hemolysis in liver disease.
Liver disease, particularly alcoholic cirrhosis, is associated with a number of interesting chemical changes which result in structural and metabolic abnormalities of the erythrocyte membrane leading to microscopically observable cell shape changes and hemolytic anemia varying from very mild to potentially lethal. Increase in unesterified serum cholesterol owing to lecithin cholesterol acyl transferase (LCAT) deficiency in cirrhosis leads to expansion of the lipid bilayer and macrocytosis without megaloblastic changes in precursors. Substitutions of phosphatidyl choline (PC) moieties in the erythrocyte lipid bilayer lead to echinocytes (disaturated PC) or to stomatocytes (diunsaturated PC). In some patients, high density lipoprotein (HDL) abnormalities lead to erythrocyte surface changes causing rapid formation of echinocytes. The rapidity and reversibility of these changes suggest blockade of metabolic transport channels critical to the maintenance of erythrocyte membrane shape. Metabolic changes involving vitamin E deficiency leading to lipid peroxidation and pyruvate kinase instability leading to adenosine triphosphate (ATP) reduction have also been invoked to explain hemolysis associated with acute liver damage. The most severe hemolysis in liver disease is associated with acanthocytes (spur cells) and a marked imbalance in cholesterol-phospholipid ratio. These patients usually have hypersplenism, as well as rigid erythrocyte membrane transformations which are irreversible. Any of the other erythrocyte membrane shape changes described appear to be reversible if the liver disease abates, but they too may become irreversible if bits of projecting membrane are repeatedly removed by the macrophages of an enlarged spleen.
Morse
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Department of Laboratory Medicine, University of Connecticut School of Medicine, Farmington 06032.
D004907:Erythrocyte Deformability; D004912:Erythrocytes / Q000378:metabolism / Q000473:pathology*; D006461:Hemolysis; D006801:Humans; D008107:Liver Diseases / Q000503:physiopathology*