Pathoma Ch 5-RBC Disorders Flashcards
(21 cards)
pathogenesis:
Hereditary Spherocytosis
Inherited defect of RBC cytoskeleton-membrane tethering proteins
Most commonly involves spectrin, ankyrin, or band 3.1
membrane blebs are formed.
RBCs eventually consumed by splenic macrophages.
Clinical/Lab findings of
Hereditary Spherocytosis
Spherocytes with loss of central pallor (Fig. 5.7)
Increased RDW and increased mean corpuscular hemoglobin concentration (MCHC)
Splenomegaly, jaundice with unconjugated bilirubin, and increased risk for bilirubin gallstones (extravascular hemolysis)
Increased risk for aplastic crisis with parvovirus Bl9 infection of erythroid
precursors
How to diagnose Hereditary Spherocytosis?
treat?
osmotic fragility test
Tx: splenectomy
pathogenesis:
SICKLE CELL ANEMIA
AR mutation in Beta chain of Hb.
Carried by 10% of Africans
DISEASE arises when TWO abnomral Beta genes are present; resulting in > 90% HbS.
What kind of hemolysis will you see with Sickle cell anemia?
Extravascular hemolysis-Reticuloendothelial system
Intravascular hemolysis
Characteristic finding of Sickle Cell Anemia on X-ray?
Massive Erythroid hyperplasia.
Expansion of hematopoiesis into skull
in liver: hepatomegaly
Complications of Sickle Cell Anemia?
Irreversible sickling leads to complications of vaso-occlusion.
Dactylitis- swollen hands and feet. common in infants (African)
Autosplenectomy-shrunken spleen
Acute chest syndrome
Pain crisis
Consequence of autosplenectomy in Sickle cell?
Increased risk of infection with encapsulated organisms such as S. pneumoniea and H. influenzae.
Increased risk of Salmonella paratyphi
How to Dx Sickle Cell Anemia?
Hb electrophoresis to confirm the presence of HbS!!
MCC of death in children with Sickle cell?
Infections due to H. influenzae (autosplenectomy)
How does someone get Sickle Cell Trait and NOT Sickle cell disease?
If only one beta chain is mutated then less than 50% of RBCs have HbS.
Pathogenesis of PNH?
DAF is anchored onto RBC cell membrane by GPI which protects RBC from the complement system.
Acquired defect in MYELOID STEM cells resulting in absent GPI :
susceptible to destruction by complement.
PNH intravascular or extravascular? So signs of PNH?
Intravascular: hemoglobinemia, hemoglobinuria, hemoglobinsideruria.
So what cell(s) is (are) destroyed in PNH?
RBC
WBC
Platelets
defect is in myeloid stem cell!
How do you diagnose PNH?
flow cytometry to detect lack of DAF
MCC of death in in PNH?
Thrombosis because of platelet rupture.
Pathogenesis of G6PD?
X-Linked Recessive disorder resulting in a reduced half life of G6PD = cells more susceptible to oxidative stress
G6PH makes NADPH, NADPH is needed to regenerated reduced glutathione so it can neutralize H202.
No G6PD, No NADH, no reduced form of glutathoine to neutralize H202 –> intravascular hemolysis.
Are there types of G6PD?
Yes, African- mildy reduced half life
Mediterranean- markeldy reduced half life
Both likely due to protective role against falciparum malaria.
How do you screen for G6PD?
Oxidative stress causes precipitation of Hb to Heinz bodies.
These Heinz bodies are removed from RBCs by splenic macrophages: BITE CELLS.
Heinz preparation is used to screen with Heinz stain.
Pathogenesis of Immune Hemolytic Anemia
antibody mediated (IgM/IgG) destruction of RBC’s.
IgG usually extravascular hemolysis.
Associated with SLE, CLL and certain drugs
IgM usually intravascular hemolysis
Associated with M. pneumoniae and infectious mononucleosis
How do you dx Immune Hemolytic Anemia
Coombs Test!
Direct- Get pt’s RBC’s and add anti-IgG. Agglutination will occur if there were RBCs were coated with IgG.
Indirect- Get patients serum and add test RBCs. If there are Ab, they will bind the test RBCs and then add your anti-IgG. Agglutination will occur if serum antibodies were present.
