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What are some lab findings consistent with hemolysis? include increased LDH (particularly isoenzyme 1) and unconjugated (indirect) bilirubin, decreased haptoglobin, free (extracellular) hemoglobin in the blood and urine, increased urobilinogen, and urine hemosiderin.
The main component of the cytoskeleton is ... spectrin, a dimer of α and β subunits
Ankyrin (band 2.1) anchors ... spectrin to transmembrane proteins (band 3, anion exchanger proteins), whereas spectrin is bound to actin and glycophorin by protein 4.1
Alterations in any portion of the red cell membrane can reduce the normal plasticity and render erythrocytes susceptible to hemolysis.
Hereditary spherocytosis (HS) is a heterogeneous group of inherited disorders of RBC cytoskeletons, characterized by a deficiency of spectrin or another cytoskeleton component (ankyrin, protein 4.2. band 3).
The deficiency of cytoskeleton protein in HS leads to a “vertical” defect in the red cell membrane, with uncoupling of the lipid bilayer from the underlying cytoskeleton. The result is progressive loss of membrane surface area and spherocyte formation
What is the end result of pathogenesis in HS? abnormal red cells are more rigid and cannot easily traverse the spleen. While circulating through the spleen, spherocytes become “conditioned” and lose additional surface membrane before they ultimately succumb to extravascular hemolysis
HS is typically what kind of inherited trait? autosomal dominant traits and (the rare recessive cases all involve the α subunit of spectrin).
spherocytes appear hyperchromic (no central pallor)
Hyperchromatic Spherocytes are typical along with polychromasia and reticulocytosis
HS pts may appear jaundiced, and up to 50% develop cholelithiasis, with pigmented (bilirubin) gallstones
Patients with HS can be managed effectively by splenectomy, although spherocytes still persist in the circulation
osmotic fragility test measures the ability of the red blood cell to swell, a property that reflects the cellular surface-to-volume ratio.
What will occur to a spherocytic red blood cell during the osmotic fragility test? A spherocytic cell in the resting state has less membrane redundancy than a normal biconcave cell so that less water can enter before cellular rupture occurs.
A special problem in sickle cell patients due to poorly vascularized tissues is... an ankle ulcer
Most clinically relevant hemoglobinopathies are caused by point mutations in the β globin chain gene.
In the sickle cell disease, an abnormal form of what hemoglobin transforms the erythrocytes into a sickle shape upon deoxygenation. S
What constitutes hemoglobin S a point maturation in the gene for the β globin chain gene substitutes valine for glutamic acid at the sixth amino acid.
hemoglobin S transforms the cytoplasm into ... a rigid filamentous gel and leads to the formation of less deformable sickled erythrocytes leading to obstruction in microcirculation
the two primary manifestations of sickle cell disease are recurrent ischemic events and chronic extravascular hemolytic anemia.
Howell-Jolly bodies, representing nuclear remnants, are seen in patients beyond childhood and reflect hyposplenism caused by ischemic loss of splenic tissue in sickle cell
What is aplastic crisis? bone marrow fails to compensate for the high level of red cell loss in SC
What is the most frequent cause of an aplastic crisis? Parvovirus 19
What is a sequestration crisis? sudden pooling of erythrocytes, especially in the spleen, results in dec. circulating blood volume and low hemoglobin,followed by hypovolemic shock and is the most frequent cause of death early in life
Patients with sickle cell anemia have increased levels of (think liver)... unconjugated (indirect) bilirubin, which predisposes to development of pigmented bilirubin gallstones
Heterozygosity for the hemoglobin S mutations is referred to as sickle cell trait
Describe the pathogenesis of the sickle cell trait. the hemoglobin A in red cells prevents hemoglobin S polymerization, so these people’s erythrocytes do not normally sickle, unless under extreme conditions(deep sea diving). Asymptomatic, do not develop hemolytic anemia and have a normal life span.
Created by: jpop