(F) L1: RBC Disorders (Part 2: Abnormalities in the RBC Membrane) Flashcards
- The RBCs have a defect in the membrane proteins of ankyrin, band 3, a-spectrin, b-spectrin, and protein 4.2 (deficiencies)
- The cell becomes spherical and fragile leading to their premature destruction in the spleen causing anemia
- In a hypotonic solution, the water tends to enter the RBC through osmosis (reduced surface area and spherical shape)
Hereditary Spherocytosis
In the skeletal proteins of RBCs that maintain its biconcave shape, what are the primary proteins?
Clue: 2 answers
- Alpha-spectrin
- Beta-spectrin
The environment of this organ includes low pH, ATP, and glucose which promotes RBC swelling and eventual bursting
Spleen
In Hereditary Spherocytosis and Elliptocytosis, RBCs are abnormally permeable to what element?
Sodium
Hereditary Spherocytosis Lab Findings:
1. What is the normal MCHC range?
2. What is the increased (abnormal) MCHC range?
- 31-37 g/dL
- 35-38 g/dL
- The RBCs have an elliptical and oval shape due to the mutation in proteins
- Deficient for proteins a-spectrin, b-spectrin, and protein 4.1 (reduced flexibility)
- In a hypotonic solution, it is more rigid and less flexible than the normal biconcave RBC (are more distended and may undergo hemolysis/fragmentation)
- The RBCs are relatively more stable in an osmotic environment (less prone to hemolysis in both isotonic and hypertonic solutions)
Hereditary Elliptocytosis
TOF: Hereditary Spherocytosis is less severe than Hereditary Elliptocytosis
False (reverse)
Inheritance patterns:
1. Hereditary Spherocytosis
2. Hereditary Elliptocytosis
A. Autosomal Dominant
B. Autosomal Recessive
C. X-linked Dominant
D. X-linked Recessive
BOTH are A. Autosomal Dominant
- Disturbs vertical membrane interactions between transmembrane proteins underlying cytoskeleton
- Disturbs horizontal membrane interactions in the cytoskeleton
A. Hereditary Spherocytosis
B. Hereditary Elliptocytosis
- A
- B
What can be found in the PBS of Hereditary Spherocytosis?
Clue: 2 answers
- Spherocytes
- nRBCs
What can be found in the PBS of Hereditary Elliptocytosis?
Elliptocytes
TOF: Hereditary Elliptocytosis has a microcytic normochromic morphology
False (normocytic-normochromic)
- The patient develops autoantibodies against their own RBCs
- The immune system mistakenly recognizes the body’s own RBCs as foreign invaders and targets them for destruction
Autoimmune Hemolytic Anemia
- This type of Autoimmune Hemolytic Anemia is the most common type and is serologically active at 37ºC
- It destroys RBCs at body temperature
- Associated with Systemic Lupus Erythematosus (SLE) and other lymphoproliferative disorders
Warm Autoimmune Hemolytic Anemia
- This type of Autoimmune Hemolytic Anemia is serologically active at 4ºC
- RBC destruction happens at lower temperatures
- Associated with Infectious Mononucleosis (IM) and other lymphoproliferative disorders
Cold Autoimmune Hemolytic Anemia
2 Types of Cold Autoimmune Hemolytic Anemia
- The immune system produces cold agglutinins which bind to RBCs at low temperatures
- It causes RBC clumping and destruction
- Primarily idiopathic or secondary to Mycoplasma pneumoniae and SLE
Cold Agglutinin Syndrome (CAS)
2 Types of Cold Autoimmune Hemolytic Anemia
- The body produces antibodies that bind to RBCs causing destruction when exposed to cold temperatures
- Is secondary to a viral infection (e.g. Epstein-Barre virus)
Paroxysmal Cold Hemoglobinuria (PCH)
Defective Production of Heme and Globin
A defect in heme synthesis characterized by impaired heme production
Porphyria
Defective Production of Heme and Globin
A qualitative globin synthesis defect
Hemoglobinopathies
Defective Production of Heme and Globin
A quantitative globin synthesis defect
Thalassemia
- What you call diseases that involve the hemoglobin
- A collection of disease where there is a point mutation or amino acid substitution within the globin molecule
Hemoglobinopathies
Categories of Hemoglobinopathies
Refers to structural defects in the Hgb molecule
Qualitative
Categories of Hemoglobinopathies
Refers to the imbalance/underproduction in the number of globin chains
Quantitative
The most frequently occurring hemoglobinopathy
Beta-hemoglobinopathies
What is the only adult form of hemoglobin that is affected in beta-hemoglobinopathies?
HbA1
What are the 4 major groups of hemoglobinopathies?
- Alpha
- Beta
- Gamma
- Delta
Adult forms of Hgb
- 2 alpha and 2 beta
- 2 alpha and 2 gamma
- 2 alpha and 2 delta
A. HbA1
B. HbA2
C. HbF
- A. HbA1 (most predominant)
- C HbF
- B HbA2
All forms of Hgb are made up of how many globin chains?
4
Beta-hemoglobinopathies
- Both beta-genes are mutated
- HbA1 is absent
- Abnormal Hgb becomes the predominant type
- e.g. Sickle Cell Disease (Hb SS) and HbC Disease (Hb CC)
Homozygous
Beta-hemoglobinopathies
- One beta gene is normal while the other is mutated
- The amount of HbA1 is more or sometimes equal in amount than the abnormal type
- E.g. Sickle Cell Trait (Hb AS) and Hb C Trait (Hb AC)
Note: A is normal while S and C are mutated
Heterozygous
What are the genes that help create beta-globulins?
Beta-genes
- This anemia is formed when glutamic acid is replaced by valine at the 6th position of the beta-chain
- It also has 2 alpha and 2 beta chains with 146 amino acids
Sickle Cell Anemia (Hb S)
Note: The insolubility of deoxygenated Hb S causes the crescent or sickle shape
- When oxygenated, Hb S is (soluble/insoluble)
- When O2 (drops/rises), sickling happens
- Soluble (shape is still normal)
- Drops
This happens to the sickle cell molecule when it is triggered by low oxygen tension, dehydration, and acidosis
Polymerization
Peripheral Blood Smear of Sickle Cell
Which cannot be found/observed in the PBS?
1. Drepanocytes
2. nRBCs
3. Polychromasia
4. Poikilocytosis
5. Anisocytosis
6. Macrocytes
7. Howell-Jolly bodies
8. Pappenheimer bodies
9. Erythroid hyperplasia
10. Reticulocytes
None, all of these can be found (familiarize yourself)
What is abnormal in the following indices during sickle cell anemia?
A. Mean cell volume
B. Mean cell hemoglobin
C. Reticulocyte distribution width
C. Reticulocyte distribution width (increased)
Note: Retic. count is increased by 5-20%
Sickle Cell Clinical Features
This type of complication will be present in their lifetime for those with sickle cell anemia
Severe chronic hemolytic anemia
Sickle Cell Clinical Features
This is due to the blockage of trapped sickle cells in one’s capillaries
Vaso-occlusive crisis
- This test for Sickle Cell uses blood mixed with sodium metabisulfite (reducing agent) which deoxygenates Hgb
- Hb S crystallizes after deoxygenation
- Holly leaf RBCs are often found (positive result)
Sodium Metabisulfite Method
TOF: You can differentiate between sickle cell trait and sickle cell anemia using the Sodium Metabisulfite Test
False (however in sickle cell anemia, sickling happens more rapidly)
- This sickle cell test uses sodium dithionite (reducing agent) and saponin (hemolytic agent) which immediately lyses RBCs
- The Hb S and sickling Hb will form liquid crystals producing a turbid appearance (positive result)
Sodium Dithionite Tube Test
- This test is confirmatory and can further differentiate Hb S from D, G, C, and E
- The migration distance of different Hgbs are based on their charge and absorption to the agar
Hemoglobin Electrophoresis (Citrate Agar)
Abnormal Hgb
- Glutamic acid on the 6th position of the beta chain is replaced by lysine
- The structural formula is a2b2 6th GLU-LYS
- The second most abnormal Hgb
Hemoglobin C
Hgb Crystals related to Hb C
- Washington monument-like appearance; protruding from the RBC membrane
- Bar of gold appearance found within the RBC membrane
A. Hb CC
B. Hb SC
- B
- A
Usually the PBS morphology of this Hgb molecule has the ff.:
- Microspherocytes
- Target cells
- Folded RBCs
- Hb CC crystals
Hb C
With Hgb C, the ff. are true:
1. RBC indices are (normal/abnormal)
2. Reticulocyte count is slightly (decreased/increased)
- Normal
- Increased
Abnormal Hgb
- The 3rd most common abnormal Hgb
- The structural formula is a2b2 26th GLU-LYS
Hemoglobin E
Abnormal Hgb
- a2b2 121st GLU-LYS
- a2b2 6th GLU-VAL and 73rd ASP-ASN (2 amino acid substitution)
- a-68th ASN-LYS b2 (affected alpha chain)
A. Hgb G (Philadelphia)
B. Hgb C (Harlem/Georgetown)
C. Hgb O (Arab)
- C
- B
- A
Abnormal Hgb
- Deletion of 5 amino acids on the beta-chain sequence (91 to 95)
- Elongation of the alpha chain and addition of 32 amino acids
A. Hgb Gun Hill
B. Hgb Constant Spring (CS)
- A
- B
These are rarely occurring abnormal Hgbs associated with methemoglobinemia and cyanosis
M hemoglobins:
- Hb M (Saskatoon)
- Hb M (Milwaukee-1)
- Hb M (Milwaukee-2)
Familiarze yourself with the rare abnormal Hgbs associated with increased and decreased oxygen affinity (3 each)
Increased:
1. Hb Hiroshima
2. Hb Rainier
3. Hb Bethesda
Decreased:
1. Hb Agenogi
2. Hb Beth Israel
3. Hb Yoshizuka
- An inherited blood disorder that results from the mutation of α-globin chains
- A deletion of 1, 2, 3, or all of the globin chains
- Severity is classified based on the number of chains affected
Alpha-Thalassemia
Alpha-Thalassemia Classifications
- 1 out of 4 genes are deleted/non-functional
- Individuals are usually carriers and asymptomatic
- The 2 alpha globulin genes are functional
- Genotype: (- a/a a)
Silent Carrier State (a-thalassemia)
Alpha-Thalassemia Classifications
- Aka a-thalassemia minor
- 2 out of 4 genes are deleted/non-functional
- Individuals may have mild anemia but is often asymptomatic
- Hgb levels are usually lower but not severely so
- Manifests as microcytic hypochromic
- Genotype: (- -/a a) or (- a/ - a)
a-thalassemia trait
Alpha-Thalassemia Classifications
- Aka a-thalassemia intermedia
- There is a deletion of 3 out of 4 alpha genes
- Leads to moderate to severe anemia with pallor, jaundice, and splenomegaly
- Manifests as microcytic hypochromic
- Genotype: (- -/ - a)
Hgb H Disease
Alpha-Thalassemia Classifications
- Aka Hgb Bart Syndrome or a-thalassemia major
- Most severe form resulting in the deletion of 4 genes
- Leads to severe anemia and fluid accumulation in the body cavities (life-threatening in utero)
- Most do not survive beyond birth
- Genotype: (- - / - -)
Hgb B Hydrops Fetalis Syndrome
- Characterized by reduced or absent production of beta globin chains
- Caused by a mutation that affects the ß globin gene complex
Beta-Thalassemia
Beta-Thalassemia Classifications
- A mutation in 1 of the 4 beta chains (Hgb production remains normal)
- Patient has signs and symptoms
- Genotype: (B-silent/ B)
Silent Carrier State (B-thalassemia)
Beta-Thalassemia Classifications
- Aka B-thalassemia minor
- 1 normal beta gene and 1 affected beta gene
- There is mild beta globin chain deficiency
- Patients have slightly lower Hgb level
- Genotypes: (B+/B) and (B0/B)
B-thalassemia trait
Beta-Thalassemia Classifications
- Aka B-thalassemia major
- Both genes are affected
- There is severe deficiency of beta globin chains
- The most severe form typically present in early childhood
- Genotypes: (B+/B+), (B+/B0), (B+/B), and (B0/B0)
Cooley’s Anemia
Beta-Thalassemia Classifications
- Both beta globin chains are affected
- A moderate reduction of beta globin chain production leading to more pronounced anemia compared to BT minor
- Manifests as microcytic hypochromic
- Genotypes: (B-silent/B-silent), (B+/B-silent), and (B0/B-silent)
B-thalassemia Intermedia
- A group of genetic disorders that affect the enzymes within the RBCs
- These play a crucial role in the metabolic processes, especially the pathways in generating energy and maintaining structural integrity of the cells in RBCs
Red Cell Enzymopathies
- The most common enzymopathy
- An inherited condition which causes non-immune hemolytic anemia
- Is part of the pentose phosphate pathway
- Prevents oxidative damage to RBCs
- This deficiency impairs the ability of the RBCs to form NADPH resulting in hemolysis
Glucose-6-phosphate dehydrogenase (G6PD)
G6PD
TOF: When G6PD is deficient, NADPH is slightly reduced
False (none will be produced at all)
G6PD
This is used to convert glutathione in its reduced form which converts hydrogen peroxide into water
NADPH
G6PD
If this is not reduced to water, it can cause the formation of free radicals within the red cells, producing denatured hemoglobin
Hydrogen peroxide (causes oxidative stress)
G6PD
- This refers to precipitated Hgb that adheres to the cell membrane
- This inclusion is removed by the spleen creating bite cells (leads to acute hemolytic anemia)
Heinz bodies
G6PD
TOF: There are other metabolic pathways that can generate NADPH in all cells when RBCs lack NADPH-reducing enzymes
True
G6PD
Glucose-6-phosphate is oxidized to what along with the reduction of NADP to NADPH?
6-phosphogluconate
Familiarize yourself with the factors that can cause oxidative stress for G6PD positive individuals
- Infections
- Sulfa drugs
- Streptomycin
- Dilantin
- Dapsone
- Mothball exposure
- Fava beans
G6PD Variants
- The mild form
- Mildly reduced half-life of G6PD (can still produce NADPH but not as much)
- Leads to mild intravascular hemolysis with oxidative stress
African Variant
G6PD Variants
- The severe form
- Markedly reduced half-life of G6PD
- Leads to marked increase in intravascular hemolysis with oxidative stress
Mediterranean Variant
G6PD deficiency plays a protective role against this parasite for the ff. reasons:
- This parasite cannot stay in RBCs since the RBC will pretty much lyse when exposed to oxidative stress
- It can lead to its own destruction in this case
P. falciparum
G6PD deficiency is also referred to as this due to allergies involving fava beans
Favism
G6PD
What is the PBS morphology?
Normocytic Normochromic
G6PD
Which are increased and which are decreased?
- Haptoglobin
- Hemopexin
- LDH enzyme
- Free Hgb
Increased: 1 and 2
Decreased: 3 and 4
- An autosomal recessive disorder of pyruvate kinase enzyme deficiency, leading to hemolytic anemia
- Individuals can be heterozygous or homozygous (worse prognosis)
- Second most common RBC enzyme defect but the most common cause of RBC enzyme-related non-immune hemolytic anemia
Pyruvate Kinase Deficiency
- A genetic defect in the PK enzyme resulting in inefficient glycolysis
- It is the enzyme responsible for the final step in glycolysis, which is required for maintaining RBC energy (ATP) levels and morphology
- This leads to a reduction of ATP and shortened RBC lifespan leading to chronic hemolysis
Pyruvate Kinase Deficiency
What gene is mutated in Pyruvate Kinase Deficiency?
PKLR gene
Pyruvate Kinase Deficiency
The PKLR gene is located in what chromosome and region of the chromosome?
Chromosome 1q21
Pyruvate Kinase Deficiency
Familiarize yourself with the events caused by lacking ATP due to PK deficiency
- Membrane instability
- Early RBC desctruction
- Cellular dehydration
- Altered RBC shape
Pyruvate Kinase Deficiency
There is (increased/decreased) 2-3 DPG synthesis within the RBC
Increased
- The 3rd most common enzyme abnormality after G6PD and PK causing hereditary non-spherocytic hemolytic anemia
- Transmitted as an autosomal recessive trait
- Hemolytic degree is generally mild to moderate
Pyrimidine-5’-Nucleotidase Deficiency
A lack of Pyrimidine-5’-Nucleotidase can cause the accumulation of precipitated RNA within the reticulocyte causing the formation of what?
Basophilic Stipplings
