5. Spherocytosis And Lymphocytosis Flashcards
2 types of haemolytic anaemia
Inherited
Acquired
Inherited haemolytic anaemia
--> From parents (defective gene) • Glycolysis defect • Pentose p pathways • Membrane protein • Haemoglobin defect
Acquired haemolytic anciemia
–> damage to cells
• Microangiopathic haemolytic anaemia (MAHA)
• Antibody damage (Autoimmune haemolytic anaemia)
• Oxidant damage (Exposure to chemicals and oxidants)
• Heat damage (e.g. severe burns)
• Enzymatic damage (e.g. snake venom)
Haemolytic anaemia diagnosis
2 main principles
• Confirm that it is haemolysis (haemolytic anaemia) due to acute reaction or chronic disease
• Determine aetiology (cause)
Symptoms of haemolytic anaemia
--> lack of rbc presence or function • Low bp • Uncontrollable bleeding • Increased heart rate • Pain • Urinary problems
* same like any anaemia (e.g. fatigue, shortness of breath) * from haemolysis increase bilirubin (breakdown of rbc releases bilirubin) jaundice gall bladder stones
Definition of haemolytic anaemia
Haemolytic anaemia results from the abnormal breakdown (haemolysis) of red blood cells
• RBC have shorter life spans 20-30 days
• Origin of haemolytic anaemia:
- in blood vessels (intravascular haemolysis) - broken down in circulation
- in the spleen (extravascular haemolysis) - rbc cleared in spleen
Bone marrow
- The bone marrow only has a capacity to increase red cell production by around 5 to 6 fold = not enough to compensate for haemolytic anaemia
- Increased production by the bone marrow is unable to compensate and anaemia will occur
- symptoms from relatively harmless to life-threatening
3 types of jaundice
- Prehepatic
- Hepatic
- Post hepatic
Haemolytic anaemia causes pre hepatic jaundice
- More rbc broken down
- More bilirubin released ionto body
- Jaundice – yellwo skin, brain fog etc
Inherited haemolytic anemias – glycolysis defect
—> Pyruvate kinase deficiency (limit ATP production) is an inherited metabolic disorder (typically autosomal recessive but there is also a dominant form) due to:
- mutations in the PKLR gene
- Four pyruvate kinase isoenzymes, two of which are encoded by PKLR (isoenzymes L and R expressed in liver and erythrocytes, respectively)
- Since red blood cells lack mitochondria, pyruvate kinase deficiency inhibits their only metabolic pathway which can supply ATP for cellular processes.
- Patients with severe deficiency may require regular blood transfusion.
Inherited haemolytic anaemias – pentose – p pathway
—> G6PDH deficiency leads to oxidative damage
- Glucose-6-phosphate dehydrogenase (G6PDH) is an X- linked recessive inborn error of metabolism, risk of haemolytic anaemia
- G6PDH is the rate limiting enzyme of the pentose phosphate pathway which supplies reducing energy by maintaining NADPH levels.
Inherited haemolytic anaemias – pentose – p pathway
—> increase oxidative damge = increase rbc clearance
- NADPH drives numerous anabolic reactions and is required to protect against oxidative stress by maintaining the level of reduced glutathione
- The pentose phosphate pathway is the only source of reduced glutathione in red blood cells,
Inherited haemolytic anaemia – hereditary spherocytosis
• Hereditary spherocytosis is an inherited autosomal dominant disease
= resulting in abnormalities in erythrocyte membrane proteins
- Impede the ability of the cell to change shape
- Causes: Mutations in the genes coding for 4 different proteins necessary to maintain RBC normal shape
Inherited haemolytic anaemia – hereditary spherocytosis
Results in
- Local disconnection of the cytoskeleton and membrane- can’t hold biconcave shape
- reduction in membrane surface area
- production of a “spherocyte” shape instead of biconcave shape to the red blood cell lysed by spleen as spleen finds it abnormal
Inherited haemolytic anaemia – hereditary spherocytosis
Treatment
Treatment: splenectomy (partial or total)
Mechanism of spherocytosis
• Spectrin and ankyrin = useful in maintaining membrane shape
• Deficiency of these = unstable membrane
○ Reduced density of membrane skeletion
○ Release micro vesicles
○ Leads to spherocytosis – round rbc which is cleared by spleem
Symptoms of hereditary spherocytosis
- destruction of red blood cells in the spleen
- their removal from the blood stream (haemolytic anaemia)
- a yellow tone to the skin (jaundice)
- an enlarged spleen (splenomegaly) and gall stone development.
Normal haemoglobin structure
The haemoglobin molecule consists of a tetramer of:
• four globin polypeptide chains
• two alpha chains and two non-alpha chains (β, δ or γ)
• held together by noncovalent interactions with each globin chain complexed with an oxygen binding haem group (that carries oxygen)
3 types of haemoglobin
HbA
HbA2
HbF
Chain compositions of HbA
- 2 alpha chains 2 beta chains
* 95% in adults
Chain compositions of HbA2
- 2 alpha and 2 delta chains
* 2-3.5%
Chain compositions of HbF
- Fetal
- 2 alpha and 2 gamma chains
- Less than 2%
Haemoglobinopathies
Definition
—> Haemoglobinopathies are inherited disorders where expression of one or more of the globin chains of haemoglobin is abnormal
Haemoglobinopathies
2 main categories:
Abnormal haemoglobin variants
Thalassaemias
Abnormal haemoglobin variants
from mutations in the genes for α or β globin chains that alter the stability and/or function of haemoglobin (e. g. Sickle cell disease)
• qualitatove – reducction in haemoglobin quality
Thalassaemias
result from reduced or absent expression of normal α or β-globin chains. This leads to a reduced level of haemoglobin rather than the presence of an abnormal haemoglobin
• Quantititaitive reduced expression of haemaglobin chaisn
Sickle cell disease - definition
—> Most common Hb variant of clinical significance is haemoglobin S (HbS)
• The HbS variant has an uncharged valine instead of a charged glutamic acid at position 6 of β-globin (glutamic acid –> valine)
Sickle cell disease impact on haemoglobin
• More prone to polymerise at low oxygen tension.
= Leads to formation of long twisted haemoglobin polymers (more insoluble) causing deformation the red blood cell membrane leading to the sickle shape
• Sickle shape – is stickier (more blockages in vasculature) and less flexible than biconcave disc
- After repeated episodes of sickling (blocking in vasculature), damage occurs to the red cell membrane causing it to lose elasticity
- Damaged cells fail to return to a normal shape when normal oxygen tension is restored
HbS variants are found in people of
– Black African descent
– Arab
– Mediterranean
– South Asia population
• Two HbS types:
- Heterozygous individuals for HbS have some resistance to malaria
- Homozygous individual develop sickle cell disease – Combinations with other haemoglobinopathies produce sickling syndromes of variable severity such as: sickle-β-thalassaemia, HbS/C or HbS/E.
Symptoms of sickle cell
Severe pain is a first-hand symptom of this disease = due to sickleing (blockages in vasculature
4 patterns of the acute sickle cell disease crisis:
- Bone crisis
- Acute chest syndrome
- Joint crisis
- Impaired organs – (e.g. lungs, eyes, kidneys, genitals, liver, spleen, heart attacks can even occur
• Enlarged spleen as the spleen works to clear out these defective rbc
Sickle cell crisis treatment
- Opioid pain medication such as morphine
- Antibiotics for infection
- Anti inflammatory medicines such as ibuprofen
- Oxygen – oxygenated blood
- Intravenous or oral fluids
- An exchange transfusion:
– conducted with a special machine
– with the help of which the abnormal sickle red blood cells are removed and replaced with normal ones - Hydroxyurea can decrease the frequency and severity of crisis
- Haematopoietic stem cell transplantation is the only cure (rarely performed – hard to find donor with sufficient genetic match)
Beta thalaseeamia
- β-thalassaemia results from mutation in one or both of the β globin genes
- Leads to a reduction in the amount or total absence of the β globin polypeptide chain
Heterozygous Beta thalaseeamia
• In heterozygous individuals where only one of the two β globin genes are mutated:
– the rate of β globin production is reduced resulting in microcytosis
OR
• Hb level normal (reduced only in pregnancy or infections)
What is Beta thalassaemia major
—> In Homozygous individuals both β globin genes are mutated, is a lifethreatening condition called β- thalassaemia major.
• Synthesis of the β globin polypeptide chain is totally absent in such individuals
Patients with Beta thalassaemia major
- Dependent on blood transfusions from the first few months of life onwards in order to survive since the synthesis of haemoglobin A cannot replace Haemoglobin F due to the lack of β globin
- Don’t have healthy production of haemoglobin
Alpha thalassaemia
• α-thalassaemia results from deletion or loss of function of one or more of the four α globin genes
Severity of Alpha thalassaemia
• The severity of the condition depends on how many genes are malfunctional ranging from:
– mild microcytosis when one or two genes are affected
– to death in utero where malfunction of all 4 genes leads to a complete absence of the α globin chain (HbF can’t switch to HbA)
• Haemoglobin H disease
Lack of function in 3 of the 4 α globin genes: • severe microcytosis • Anaemia • haemolysis • (enlarged spleen) splenomegaly
Severity of thalassemia
Different combinations of α and β globin mutations in the same individuals lead to a wide range of thalassaemia phenotypes (differences in the severity of disease):
3 types of thalassemia severity
- Patients can either be transfusion dependent (thalassaemia major),
- require transfusion intermittently (thalassaemia intermedia) or
- require no transfusion (thalassaemia minor).
Acquired haemolytic anaemias
- Microangiopathic haemolytic anaemia (MAHA)
- Antibody damage (Autoimmune haemolytic anaemia)
- Oxidant damage (Exposure to chemicals and oxidants)
- Heat damage (e.g. severe burns)
- Enzymatic damage (e.g. snake venom)
Microangiopathic haemolytic anaemias (MAHA) - cause
- CAUSE: where red cells are damaged by physical trauma.
- Often trauma results from red cells getting snagged as they try to pass through small vessels (so their shape changes) laden with fibrin strands because of increased activation of coagulation
- Microangiopathic haemolytic anaemias (MAHA)
Effects
Increased activation of coagultaion is caused by
- Disseminated intravascular coagulation: a condition where bleeding and clotting occur at the same time in the patient (e.g. in malignancy, obstetric complications, trauma, sepsis, haemolytic uremic syndrome (HUS)in children) can cause this
- Thrombotic thrombocytopenic purpura - (microangiopathic haemolytic anaemia) a syndrome where small thrombi (clots) within the microvasculature.
Antibody damage (Autoimmune haemolytic anaemia)
Causes
– Infections
– lymphoproliferative disorders such as leukaemia or lymphoma
– Reactions to drugs such as cephalosporins (class of antibiotic)
2 types of Antibody damage (Autoimmune haemolytic anaemia)
- In warm autoimmune haemolytic anaemia (happens in temp <37 degrees)
- In cold autoimmune haemolytic anaemia (temp less than 37 degrees)
• 1. In warm autoimmune haemolytic anaemia (happens in temp <37 degrees)
○ IgG antibodies recognise epitopes on the red cell membrane.
○ This leads to macrophages in the spleen recognising these red blood cell, destroy RBC or can become membrane spherocytes splenomegaly (enlarged spleen)
• 2. In cold autoimmune haemolytic anaemia (temp less than 37 degrees)
○ IgM autoantibodies recognise red cell epitopes and there is also complement fixed to the patient’s red cells leading to membrane instability and lysis:
○ Results in – numb fingertips, earlobes etc. (peripheral body parts) – pallor (paleness), – blue discoloration or – in extreme cases gangrene
Test for autoimmune haemolytic anaemia
The direct Coombs test
—> Detect antibodies or complement bound to the surface of red blood cells.
Positive test
• The patient’s red cells are mixed with anti-human globulin antibody
• If the red cells are coated with antibodies the anti-human globulin will attach to those antibodies making the red cells clump together suggesting the patient’s haemolytic
4 Other causes of haemolysis
- Oxidant damage (Exposure to chemicals and oxidants) e.g. lead poisoning
- Heat damage (e.g. severe burns)
- Enzymatic damage (e.g. snake venom) and
- even “foot strike haemolysis” in runners
Myeloproliferative Neoplasms (MPNs)
Definition
—> Group of diseases of the bone marrow in which excess cells are produced
Myeloproliferative Neoplasms (MPNs)
Cause
- Specific point mutation in one copy of the Janus kinase 2 gene (JAK2) - a cytoplasmic tyrosine kinase on chromosome 9, which causes increased proliferation and survival of haematopoietic precursors
- Increase of precursors in circualtion
TPO – thromboperitin
• Stimulates platlets
EPO – erythropoietin
• Stimulates rbc
4 major types of Myeloproliferative Neoplasms (MPNs)
- Polycythaemia vera – looking at rbc
- Essential thrombocythemia – looking at platlets
- Primary myelofibrosis – looking at bone marrow
- Chronic myeloid leukaemia
Production of platelets
- Stimulation of TPO thromboperitin
* Increase in megakaryocyte = increase in platlets
Polycythaemia - definition
—> Increase in circulating red cell concentration typified by a persistently raised haematocrit (Hct).
Polycythaemia - 2 types
Relative
Absolute
Relative polycythaemia
○ Decrease in plasma volume
○ Makes it appear that ratio of rbc is higher
Absolute polycythaemia
• Increase in number of erthrythrocytes
○ Primary = abnormality originates in bone marrow, polycythaemia vera only example
○ Secondary = caused by increased levels of erythropoietin due to:
▪ Physiological response to hypoxia e.g. high altitude, chronic lung disease
▪ Abnormal production e.g. renal carcinoma, renal artery stenosis
Polycythaemia vera
–> increase in rbc in circulation
- Disease in which the volume percent of erythrocytes in the blood (the haematocrit) exceeds 52% (males) or 48% (females).
- Most (~95%) cases are caused by mutation of the gene coding for Janus Kinase 2 (JAK2)
Clinical features of polycythaemia vera
- Thrombosis = increase in rbc, increase viscosity, abnormal blood flow
- Haemorrhage
- Headache
- Burning pain in the hands or feet
- Pruritus
- Splenic discomfort, splenomegaly
- Gout = uric acid is a breakdown product of rbc
- Arthritis
- May transform to myelofibrosis or acute leukaemia
Extra rbc stimulate histamine = itchy
Management of polycythaemia
- Phlebotomy = blood letting, remove some rbc
- Aspirin = reeduce blood viscosity
- Cytoreduction using agents such as hydroxycarbamide (oral antimetabolite that inhibits DNA synthesis)- slows down cell production
Thrombocytosis
—> An increase in the platelet count compared to the normal range of a person of the same gender and age
3 types of thrombocytosis
Primary
Secondary
Redistribution
Primary Thrombocytosis
○ Originates in bone marrow = essential thrombocythemia
Secondary Thrombocytosis
○ Normal bone marrow resposne to extrinsic stimulus (e.g. infection, inflammation)
Redistribution Thrombocytosis
○ Platelets redistributed from splenic pool into bloodstream
Essential thrombocythaemia (primary)
Causes
• Around half the cases are caused by JAK2 mutations
• Mutations in the thrombopoietin receptor can also result in the disease
= continuously active = more platlets
Essential thrombocythemia (primary) - clinical feature
- Numbness in the extremities
- Thrombosis
- Disturbances in hearing and vision (related to microvascular complications)
- Headaches
- Burning pain in the hands or feet (Erythromelalgia)
Numbness and burning due to high platelets count reduces blood flow to the area
Essential thrombocythaemia (primary) Management
- Aspirin = blood viscosity
* Return the platelet count into the normal range with drug such as hydroxycarbomide
Thromobcytopenia
• An abnormally low level of platelets - either be inherited or acquired.
Not a myloproliferative disorder as the platlet number is low
Types of Thromobcytopenia
Inherited (rare syndromes)
Acquirred
○ Decreased platelet production due to:
○ Increased platelet consumption (platelets are used more) due to:
○ Increased platelet destruction due to:
Acquired thrombocytopenia
○ Decreased platelet production due to:
▪ not enough B12 or folate deficiency
▪ Acute leukaemia or aplastic anaemia
▪ Liver failure (decreased thrombopoietin production)
▪ Sepsis
▪ Cytoxic chemotherapy
Acquired thrombocytopenia
○ Increased platelet consumption (platelets are used more) due to:
▪ Massive hemorrhage
▪ Disseminated intravascular coagulation – abnormal blood clotting
▪ Thromotic thrombocytopericpurpura – blood clots form in small blood vessels
Acquired thrombocytopenia
○ Increased platelet destruction due to:
▪ Autoimmune response
▪ Drug induced – heparin
▪ Hypersplenism resulting in increased destruction and splenic pooling of platlets
Thrombocytopenia clinical features
- Patients generally not symptomatic until the platelet count < 30
- Easy bruising
- Petechiae – small spots on feet/forarms
- Mucosal bleeding
- Severe bleeding after trauma
- Intracranial haemorrhage
Females have heavier periods
Heavier nose bloods
Management – thrombocytopenia
- Corticosteroids
- Intravenous pooled human Immunoglobulin
- Splenectomy
- Thrombopoietin receptor agonists
Primary myelofibrosis
—> A myeloproliferative neoplasm where the proliferation of mutated hematopoietic stem cells
= results in reactive bone marrow fibrosis eventually leading to the replacement of marrow with scar tissue (collagen deposition)
• Due to fibrosis bone marrow can’t make enough normal blood cells
• Mutations in the JAK2 gene are often associated with the disease.
Primary myelofibrosis – clinical features
- Hepatosplenomegaly – production of hematopoietic stem cells from spleen or liver
- Bruising
- Fatigue (and other symptoms related to anaemia)
- Weight loss
- Fever
- Increased sweating
- Portal hypertension
Management primary myelofibrosis
- Hydroxycarbamide
- Folic acid – stimulate platelet function
- Allopurinol – gout symptoms
- Blood transfusions – anaemia
- Splenectomy
- Ruxolitinib, an inhibitor of JAK2 has been shown to significantly reduce spleen volume and improve symptoms of myelofibrosis.
Chronic myeloid leukaemia (CML)
- Characterized by the unregulated growth of myeloid cells in the bone marrow
- Specific chromosomal translocation called the Philadelphia chromosome involving a reciprocal translocation between chromosomes 9 and 22. This translocation causes an oncogenic gene fusion (BCR-ABL)
Chronic myeloid leukaemia (CML)
2 types
- Acute = lots of immature cells (faster)
* Chronic = lots of immature and mature (diferentiated) cells (slow)
Pancytopenia
–> reduction in all blood cells
• Reduction in white cells, red cells and platelets
Pancytopenia causes
- B12/folate deficiency – required in dna synthesis
- Drugs
- Infections - Viruses
- Bone marrow infiltration by malignancy
- Marrow fibrosis
- Radiation
- Idiopathic aplastic anaemia
- Congenital bone marrow failure
Aplastic anemia
- A rare disease resulting in damage to bone marrow and hematopoietic stem cells
- Pancytopenia
4 proteins that are the most common causes of hereditary spherocytosis
- Spectrin
- ankirin
- band 3
- protein 4.2
