Disorders of Red Blood Cells Flashcards
How do you differentiate iron deficiency microcytic anemia from thalassemia microcytic anemia?
Look at the Rbc Distribution Width (RDW)
- Iron deficiency will have a High RDW
- Thalassemia will have a low RDW
In the presence of an anemia what can the reticulocyte count indicate?
In the presence of anemia a…
High count = over production or loss of storage of RBCs
Low Count = Impaired production (bone marrow destruction)
What are Howell Jolly bodies and what is it associated with?
- Nuclear remnants
- Indicative of asplenia or severe anemia
What are targets in RBCs and what is it associated with?
1) Concentrations of hemoglobin
2) Assoc. with Hemoglobin C disease, Asplenia, Liver disease, Thalassemia
think: HALT said the hunter to his target
What are Heinz bodies and what are they associated with?
- Large, blue intracytoplasmic inclusions attached to inner cell membrane that consists of precipitated hemoglobin
- Assoc. with G6PD, thalassemia, and Oxidant drugs (Primaquine and Dapsone)
What enzyme is inhibited by lead poisoning?
Ferrochelatase, ALA dehydratase, and pyrmidine 5-nucleotidase
When looking at a Red Cell Histogram what does a left shift indicate? Right?
Left = microcytic red cells Right= macrocytic red cell
How are reticulocytes identified?
Polychromasia. Granular netowrk of polyribosomes/rough ER that clump and are observed with staining.
Name the different cell types in erythropoiesis.
1) Proerythroblast
2) Basophilic erythroblast
3) Polychromatophilic erythroblast
4) Orthochromatophilic erythroblast
5) Reticulocyte
6) Erythrocyte
What is the difference between an orthophilic erythroblast and a reticulocyte?
Reticulocyte does not have a nucleus and has polychromasia
How long does it take for the body to respond to decreased rbcs due to anemia/blood loss?
7 days. It takes 5 days for maturation from stem cell to reticulocyte
What are the effects of massive bone marrow proliferation due to untreated anemia?
1) Expansion of the medulla
2) Thinning of the cortical bone
3) Resporption of cancellous bone
4) Secondary Bone Formation (prominent cheekbones and skull changes)
What is an infectious cause for pure red cell aplasia?
Parvovirus
What is the cause of basophilic stippling?
1) Thalassemia
2) Anemia of chronic disease
3) Lead poisoning
How can you differentiate sideroblastic anemia from other forms of microcytic hypochromic anemias?
Sideroblastic anemia has a high serum iron level due to the fact that this disease is caused by heme synthesis problems
What metabolites are high in a pt. with lead poisoning?
1) ALA increased in urine
2) Protoporphyrin IX in blood
Causes of macrocytosis anemia?
1) Rapid RBC turnover (increased reticulocytes)
2) Chronic alcoholism
3) Megaloblastic anemia
4) Orotic aciduria
What lab value do you use to confirm B12 deficiency?
Serum Homocysteine or methylmalonic acid (should be elevated)
What does hemoglobin in the urine, decreased haptoglobin, and increased bilirubin indicate?
Intravascular hemolysis
What is a positive Coomb’s test indicative of?
Autoimmune hemolytic anemia
How can you differentiate extravascular from intravascular hemolysis?
1) Intravascular will have hemoglobinemia, hemoglobinuria, and hemosiderinuria.
2) Jaundice is found in both
3) Increased erythropoietin
Autosomal dominant disease of rbc that is due to an insufficiency of membrane skeletal proteins which results in a lack of deformability resulting in hemolysis
Hereditary Spherocytosis
What proteins are affected in hereditary spherocytosis?
1) Spectrin
2) Ankyrin
3) Band 3
What is the primary cause of hemolysis in hereditary spherocytosis?
The spleen. Cell are not able to pass through the cords of Billroth
What is the most likely cause of aplastic crises in a pt. with Hereditary Spherocytosis?
Parvovirus infection. This occurs because virus targets erthroprogenitor cells. Leads to decreased erythropoeisis which is constantly required for HS
What reaction is glucose 6 phosphate dehydrogenase involved with?
Reaction: Glucose 6 phosphate –> 6-phosphogluconate
Reduces NADP –> NADPH
What X linked disease results in episodic hemolysis due to a misfolding of an important protein involved with glutathione pathway which releives oxidative stress?
Glucose 6 phosphate dehydrogenase deficiency
What is the cause of episodic hemolysis in G6PD deficiency? What initiates this?
Oxidative stress
1) Infections
2) Typhoid fever
3) Oxidant drugs (sulfonamides, anti-malarials)
4) Fava beans
How do Heinz bodies form in G6PD deficiency?
The increased in oxidative stress results in the crosslinking of sulfhydrl groups which precipitate at the membrane resulting in dark inclusions known as Heinz bodies
Why is episodic hemolysis observed in G6PD deficiency?
1) Because hemolysis only occurs in older rbcs
Older cells = decreased enzymes (do not produce)
Younger cells= normal amount of enzymes
What autosomal recessive disease results in chronic hemolysis due to a defect in a protein involved with the conversion of phosphoenol pyruvate to pyruvate?
Pyruvate Kinase Deficiency
Why does Pyruvate kinase deficiency cause hemolysis?
The absence of the conversion of phosphoenol pyruvate to pyruvate results in a decrease in ATP.
Decreased ATP leads to loss of membrane integrity
What are Schistocytes and what are they associated with?
1) Fragmented RBCs due to mechanical trauma
2) Associated with Stenotic valve, DIC, TTP/HUS
Why do children have skull deformities with chronic untreated anemia and adults do not?
Children already have hematopoeisis going on throughout body so it must expand in the skull. Adults just turn on hematopoeisis within the long bones
What are causes of hypochromic microcytic polychrmoasia anemia?
1) Beta Thalassemia
2) Treated iron deficiency
What is the mutation that causes sickle cell anema (HbS)?
1) Point mutation of the 6th codon in the beta globin 2) Results in replacement of glutamate with valine
What is the mutation found in HbC?
1) Point mutation of the 6th codon in the beta globin
2) Results in replacement of glutamate with lysine
3) Increases sickling in sickle cell trait
How does the Sickle shape form in Sickle cell anemia?
When HbS becomes deoxygenated it results in polymerization and aggregation that causes the cytoplasm to become viscous. Together these cause a sickle shape
What four factors influence sickling of rbcs?
1) Interaction with other hemoglobin
2) Intracellular pH
3) Mean cell hemoglobin concentration
4) Transit time through microvascular beds
What determines the severity of chronic hemolysis in Sickle cell anemia?
1) The percentage of irreversibly sickled cells
What is the difference in where spherocytes and sickle cells are captured in the spleen?
1) Spherocytes = cords of Billroth
2) Sickle cells = cords and sinusoids
How does autosplenectomy, a common occurnence in Sickle cell patients, occur?
1) It occurs by chronic erythrostasis that leads to splenic infarction, fibrosis, and progressive shrinkage
Clinical features of Sickle cell disease
1) Severe hemolytic anemia
2) Vaso-occlusive (pain) crises - common in bone, brain, liver, lungs, spleen
3) Sequestration crises (in children with intact spleens)- causes massive splenomegally
4) Aplastic crises - occurs with Parvovirus infx
5) Chronic hypoxia- results in impaired growth and development
6) Hyposthenuria (unable to concentrate urine)
7) Increased susceptibility to encapsulated organisms
8) Gall stones
What is used to treat Sickle cell anemia and why?
1) Hydroxyurea
2) Inhibits DNA synthesis resulting in an increase in HbF and an anti-inflammatory effect due to a decrease in wbc production
What is the cause of ineffective erythropoeisis in beta thalaseemia?
1) The accumulation of alpha globins results in membrane damage causing ineffective erythropoeisis
What are the complications of ineffective hematopoiesis for those with severe beta thalassemia?
1) It causes extramedullary hematopoiesis
2) Also leads to increase in absorption of dietary iron leading to iron overload
3) Iron overload complicates blood transfusions
What are the two clinical syndromes of beta thalassemia?
1) Beta thalassemia major - requires blood transfusions, generally homozygous, results in severe ineffective hematopoeisis; HbF major
2) Beta thalassemia minor - usually asymptomatic or mild anemia; generally heterozygous; HbA2 major
What are the four clinical syndromes of alpha thalassemia?
1) Silent Carrier State (1 deletion)
2) Alpha Thalassemia trait (2 deletions)
3) Hemoglobbin H Disease (3 deletions)
4) Hydrops fetalis (4 deletions)
What type of tetramers form in Hemoglobin H disease?
HbH - tetramer of beta globin; high affinity for oxygen; forms with deletion of 3 alpha genes
What type of tetramers form in Hydrops fetalis?
Bart’s hemoglobin- tetramer of gamma globin; deletion of all four alpha genes
What is Hemoglobin SC disease?
It is a combination of HbS and HbC that increases sickling
What disease is due to an X linked, acquired, mutation that results in increased complement mediated RBC lysis?
Paroxysmal Nocturnal Hemoglobinuria (PNH)