Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0002895 (sickle cell disease)
 11,747 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Coagulation abnormalities are frequently reported in hemolytic anemias (HA). Several pathophysiologic mechanisms are common to different HA. In this review three different hemolytic disorders will be discussed. In sickle cell disease and in beta-thalassemia, a thrombophilic status has been well documented as multifactorial involving hemostatic changes and activation of the coagulation cascade. Moreover, in such disorders, elevated levels of endothelial adhesion protein (ICAM-1, ELAM-1, VCAM-1, von Willebrand factor, and thrombomodulin) are often increased, suggesting that endothelial activation may be involved in vascular occlusion. As an additional mechanism of hypercoagulability in thalassemia, a procoagulant status of thalassemic red cells was recognized. The main clinical manifestation of paroxysmal nocturnal hemoglobinuria (PNH) is HA, and the most common complications are thrombosis, pancytopenia, and myelodysplastic syndrome or acute leukemia. The intravascular hemolysis is explained by a deficiency of glycosil phosphatidylinositol (GPI)-anchored complement regulatory proteins such as CD59 and CD55 on the membrane of red blood cells (RBCs), but the mechanism responsible for the increased incidence of thrombotic events in PNH remains unclear. Recent advances have been made in understanding the coagulation involvement in a heterogeneous group of diseases, thrombotic microangiopathies (TMA) characterized by microangiopathic hemolytic anemia and thrombocytopenia due to platelet clumping in the microcirculation, leading to ischemic organ dysfunction with neurologic symptoms and renal impairment.
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PMID:Coagulation in the pathophysiology of hemolytic anemias. 1802 12

The complement system is an innate immune defense cascade that can cause tissue damage when inappropriately activated. Evidence for complement over activation has been reported in small cohorts of patients with sickle cell disease (SCD). However, the mechanism governing complement activation in SCD has not been elucidated. Here, we observe that the plasma concentration of sC5b-9, a reliable marker for terminal complement activation, is increased at steady state in 61% of untreated SCD patients. We show that greater complement activation in vitro is promoted by SCD erythrocytes compared to normal ones, although no significant differences were observed in the regulatory proteins CD35, CD55, and CD59 in whole blood. Complement activation is positively correlated with the percentage of dense sickle cells (DRBCs). The expression levels of CD35, CD55, and CD59 are reduced in DRBCs, suggesting inefficient regulation when cell density increases. Moreover, the surface expression of the complement regulator CD46 on granulocytes was inversely correlated with the plasma sC5b-9. We also show increased complement deposition in cultured human endothelial cells incubated with SCD serum, which is diminished by the addition of the heme scavenger hemopexin. Treatment of SCD patients with hydroxyurea produces substantial reductions in complement activation, measured by sC5b-9 concentration and upregulation of CD46, as well as decreased complement activation on RBCs in vitro. In conclusion, complement over activation is a common pathogenic event in SCD that is associated with formation of DRBCs and hemolysis. And, it affects red cells, leukocytes and endothelial cells. This complement over activation is partly alleviated by hydroxyurea therapy.
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PMID:Complement activation in sickle cell disease: Dependence on cell density, hemolysis and modulation by hydroxyurea therapy. 3199 Mar 87