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44 Cards in this Set

  • Front
  • Back
erythrocyte membrane allows for
selective permeability and deformity
2 interrelated parts of RBC membrane
1. outer lipid bilayer w/ embedded proteins
2. underlying membrane proteinaceous skeleton
role of lipid bilayer
serves as selective barrier, allowing only necessary molecules entry and exit
role of protein membrane skeleton
provides RBC its characteristic shape, structure, and deformability
defects in membrane components of RBC manifest as:
differences in shape and deformability -/+ permeability to certain molecules
general considerations of RBC membrane defects
1. variable clinical presenations and severities
2. if symptomatic include: anemia, jaundice, and splenomegaly
3. hemolysis is extravascular (in the spleen)
hereditary spherocytosis:
inheritance
AD
hereditary spherocytosis:
defect in protein composition
and effect
ankyrin
spectrin
band 3
protein 4.2
-vertical
-disconnect the lipid bilayer from underlying cytokeletal proteins
hereditary spherocytosis:
clinical findings
anemia
jaundice
splenomegaly
hereditary spherocytosis:
lab findings
-spherocytes on peripheral smear
-inc #s of reticulocytes
-unconjugated bilirubin
-dec haptoglobin
-inc osmotic fragility
hereditary spherocytosis:
tx
splenectomy
hereditary elliptocytosis:
inheritance
AD
hereditary elliptocytosis:
protein defect and its effect
spectrin
protein 4.1
-horizontal
-inability of spectrin dimers to form tetramers and oligomers
hereditary elliptocytosis:
clinical findings
variable
asymptomatic
significant hemolytic anemia: anemia, jaundice, splenomegaly
hereditary elliptocytosis:
lab findings
-unconjugated hyperbilirubinemia
-dec haptoglobin
-
hereditary elliptocytosis:
tx
most do not require tx
splenectomy for some
hereditary pyropoikilocytosis:
inheritance
AR
hereditary pyropoikilocytosis:
protein defect and effects
spectrin
-impair conversion of dimers into tetramers and oligomers
-partially deficient in spectrin due to dec synthesis -/+ increased degradation
hereditary pyropoikilocytosis:
clinical findings
present in neonatal period with hemolytic anemia and jaundice
hereditary pyropoikilocytosis:
lab findings
-RBC with marked thermal sensitivity
-bizarre shaped and microcytic cells
hereditary pyropoikilocytosis:
tx
transfusion and phototherapy
hereditary stomatocytosis:
inheritance
AD
hereditary stomatocytosis:
protein defects and effects
stomatin
-intergral membrance protein is dec or absent
-abnormal RBC membrane permeability which leads to either hydrocytosis (inc MCV) or xenocytosis (dec MCV)
hereditary stomatocytosis:
hydrocytosis
failure of Na/K pumps leads to elevated erythrocytoic Na content and cell water
hereditary stomatocytosis:
xenocytosis
lose K+, but mechanism is unknown
hereditary stomatocytosis:
lab findings
hydro: macrocytic and inc osmotic fragility

xeno: dec osmotic fragility

mouth-shaped area of central pallor
hereditary stomatocytosis:
clinical findings
variable severities of permeability defects, stomatin deficiency, hemolysis, anemia, and # of stomatocytes
-marked predisposition to thrombotic episodes after splenectome (inc erythrocyte-endothelial cell adhesion)
metabolically based anemias cause
underlying disorders of internal RBC metabolism

-increased RBC destruction and hemolytic anemia
erythrocytes depend on what sources of energy
1. anaerobic: EMP, glycolysis
2. aerobic: PPP
primary purpose of PPP
only 2 molecules of ATP
10% of RBC glucose

-supply reducing potential to the cell, by generating NADPH
-NADPH: generating glutathione, which reduces oxidized sulfhydrl groups in Hb
PK: defect in which system
EMP/glycolysis
G6PD: defect in which system
PPP
PK deficiency:
inheritance
AR
most are homozygous or double hetero for 2 mutant genes
PK deficiency:
metabolic defect and effect
reduced activity (not absence)
-marked reduction in ATP production which leads to impairment of Na/K ATPase pump

-K is lost, along with water - cell shrinkage and distortion of shape; distorted are destroyed prematurely
PK deficiency:
compensatory effect
inc production of 2,3-DPG which increases 2-3 fold in PK pts
-increased capability to release oxygen to the tissues, inc exercise capacity, dec symptoms
PK deficiency:
clinical features
variable
-requiring transfusions
-asymptomatic
anemia, splenomegaly, jaundice, gallstones
PK deficiency:
lab findings
no prominent morphological features
-elevated unconj bili
-dec haptoglobin
G6PD deficiency:
inheritance
X-linked recessive
G6PD deficiency:
metabolic defect and effect
G6PD is important for NADPH production which regenerates reduced glutathione which is necessary to protect RBCs from oxidative stress (detoxifies H2O2 and free radicals, protecting enzymes and Hb from oxidation)

-if deficient: Hb is denatured and membrane thiols are oxidized forming heinz bodies
-heinz bodies attach to membrane sulfhydryls and induce cell rigidity
G6PD deficiency:
lab findings
-heinz bodies
-hemoglobinuria
-dec haptoglobin
-bite cells
G6PD deficiency:
clinical findings
hemogloinuria
jaundice
what is favism
manifests with a sudden onset of acute hemolysis 24-48 hours after ingestion of fava beans (in small % of G6PD pts)
favism:
signs of disorder
hemoglobinuria
favism:
tx
supportive
transfusion