Download Module III: BLOOD AND IMMUNITY

Module III: BLOOD AND IMMUNITY;
WEEK 2
LEARNING OBJECTIVES:
By the end of the second week of module III, student should able to:

Correlate the changes in structure and function of the different types of Hemoglobin in
health and in disease states.

Correlate different Hb electrophoresis pattern

Relate normal and abnormal haemostatic mechanisms with the coagulation cascade

Relate blood and blood components transfusion and transfusional reactions
CLINICAL CASE
Moula Bux and his wife are sitting in the waiting room of their family physician, Dr.
ABC. They are a young couple, who are first cousins and have been married for just two
years and have a son, Sumar, whom they have brought in for a follow-up visit to the
doctor. They are concerned because Sumar has recently been suffering from repeated
infections. Although the boy seemed to be a happy and healthy newborn, he has grown
increasingly listless over the past few months. He has lost much of his appetite and his
complexion has become pale. The parents believe that their son has become anemic due
to his poor diet; both Moula Bux and his wife themselves suffered from jaundice as
babies.
The family is called in to see the physician , who, after exchanging pleasantries, reviews
the boy’s symptoms and examines him . On examination he is short statured and pale.
He has prominent facial and frontal bones. His spleen is enlarged and palpable 4cm
below his left costal margin. The blood reports reveal:
Table 1. Blood Sample Results
Hemoglobin (Hb)
5.2g/dL
MCV
59fl
MCHC
25
1
WBC
4,200
Platelets
3,89,000
Reticulocyte count
4.8%
Hypochromic, microcytic red cells ,
target cells, nucleated red cells ,
polychromasia
Questions:
1.
2.
3.
4.
5.
6.
7.
How can the physical signs be explained?
Why is the boy short statured and have prominent facial and frontal bones?
Why the spleen is enlarged?
Analyze the blood report?
Why reticulocyte count increases against low MCV?
What is the most likely condition child is suffering from?
What condition could thalassemia be confused with on the basis of the red cell
indices?
8. How do these parameters (red cell indices) change in anemia of chronic disease
and iron deficiency anemia?
9. Why patients of thalassemia are asymptomatic at birth?
10. Role of interfamily marriages in thalassemia?
11. What further advised you give to the parents?
12. What is the mode of hereditary transmission for this disease?
13. What is Hb F? Wow does it differ from adult hemoglobin?
14. What is the ultimate prevention?
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Assignment:
Visit to thalassemia centre
Microscopic identification of red cells (normal and abnormal)
Assessment:
BCQ’S with case based scenerio
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FACILATATOR’S GUIDE:
The thalassemias are a group of inherited hematologic disorders caused by defects in the synthesis of
one or more of the hemoglobin chains. Alpha thalassemia is caused by reduced or absent synthesis of
alpha globin chains, and beta thalassemia is caused by reduced or absent synthesis of beta globin
chains.
The thalassemias are a group of inherited autosomal recessive hematologic disorders that cause
hemolytic anemia because of the decreased or absent synthesis of a globin chain. Imbalances of globin
chains cause hemolysis and impair erythropoiesis.
Approximately 5 percent of the world's population has a globin variant, but only 1.7 percent has alpha or
beta thalassemia trait. Beta thalassemia is most common in persons of Mediterranean, African, and
Southeast Asian descent.
Pathophysiology.
Hemoglobin consists of an iron-containing heme ring and four globin chains: two alpha and two non alpha.
The composition of the four globin chains determines the hemoglobin type. Fetal hemoglobin (HbF) has
two alpha and two gamma chains (alpha2gamma2. Adult hemoglobin A (HbA) has two alpha and two beta
chains (alpha2beta2), whereas hemoglobin A2 (HbA2) has two alpha and two delta chains (alpha 2delta2). At
birth, HbF accounts for approximately 80 percent of hemoglobin and HbA accounts for 20 percent. The
transition from gamma globin synthesis (HbF) to beta globin synthesis (HbA) begins before birth. By
approximately six months of age, healthy infants will have transitioned to mostly HbA, a small amount of
HbA2, and negligible HbF. Anemia in beta thalassemia is generally caused by the presence of two
interrelated phenomena: death of red blood cell (RBC) precursors within the bone marrow (ineffective
erythropoiesis, also called intramedullary hemolysis) and increased destruction of circulating RBCs
(hemolytic anemia). Hemolysis in beta thalassemia is intracorpuscular (ie, due to abnormalities primarily
within the red cell) and extravascular (ie, occurring in the monocyte-macrophage system); as a result, there
is little hemoglobinemia or hemoglobinuria. In addition to the presence of abnormal RBC size due to
decreased overall hemoglobin production (ie, hypochromia and microcytosis), there are, depending upon
the phenotype, grossly abnormal RBC shapes including target cells, tear-drop cells (dacrocytes),
fragmented forms, echinocytes, and the presence of RBC inclusions .
Beta thalassemia is the result of defcient or absent synthesis of beta globin chains, leading to excess alpha
chains. Beta globin synthesis is controlled by one gene on each chromosome 11.
Table 2: Prototypical Forms of Beta Thalassemia
Variant
Chromosome 11
Signs and Symptoms
Beta
One gene defect
thalassemia trait
Asymptomatic
Beta
thalassemia
intermedia
Two genes defective (mild to
moderate decrease in beta
globin synthesis)
Variable degrees of severity of symptoms of
thalassemia major
Beta
thalassemia
major
Two genes defective (severe
decrease in beta globin
synthesis)
Abdominal swelling, growth retardation, irritability,
jaundice, pallor, skeletal abnormalities, splenomegaly;
requires lifelong blood transfusions
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Table 3: Hematologic Indices of Iron Deficiency, Alpha and Beta Thalassemia and Anemia of
Chronic illness
Anemia of
chronic
illness
Iron
deficiency
Beta
Alpha
thalassemia thalassemia
MCV (abnormal if < 80 fl in adults; < 70 fl In
children six months to six years of age; and < 76 fl
in children seven to 12 years of age)
Low
Low
Red blood cell distribution width
High
Normal;
Normal
occasionally
high
Normal
Ferritin
Low
Normal
Normal
Normal
Mentzer index for children (MCV/red blood cell
count)
> 13
< 13
< 13
< 13
Hb electrophoresis
Normal (may
have reduced
HbA2)
Increased
HbA2,
reduced
HbA, and
probably
increased
HbF
Adults: normal
Normal
Test
Low
Low or
Normal
Newborns: may
have HbH or or
Hb Bart's
Hb = hemoglobin; HbF = fetal hemoglobin; MCV = mean corpuscular volume.
The hemoglobin electrophoresis with beta thalassemia trait usually has reduced or absent HbA, elevated
levels of HbA 2, and increased HbF. Persons with beta thalassemia major are diagnosed during infancy.
Pallor, irritability, growth retardation, abdominal swelling, and jaundice appear during the second six
months of life.
The complications that occur with beta thalassemia major or intermedia are related to overstimulation
of the bone marrow, ineffective erythropoiesis, and iron overload from regular blood transfusions.
Untreated infants have poor growth, skeletal abnormalities, and jaundice.
With multiple blood transfusions and continued absorption of intestinal iron, iron overload develops.
Iron is deposited in visceral organs (mainly the heart, liver, and endocrine glands), and most patient
deaths are caused by cardiac complications. Endocrinopathies, particularly hypogonadism and diabetes
mellitus, may occur in adolescents and adults.
Splenomegaly invariably develops in the symptomatic thalassemias. Splenomegaly can worsen the
anemia and occasionally cause neutropenia and thrombocytopenia.
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Persons with thalassemia trait require no treatment or long-term monitoring. They usually do not have
iron defciency, so iron supplements will not improve their anemia. Accordingly, iron therapy should
only be administered if iron defciency occurs.
Persons with beta thalassemia major require periodic and lifelong blood transfusions to maintain a
hemoglobin level higher than 9.5 g per dL (95 g per L) and sustain normal growth.
Transfusion-dependent patients develop iron overload because they have no physiologic process to
remove excess iron from multiple transfusions. Therefore, they require treatment with an iron chelator
starting between five and eight years of age. Deferoxamine (Desferal), subcutaneously or intravenously,
has been the treatment of choice.
Bone marrow transplantation in childhood is the only curative therapy for beta thalassemia major
Preconception genetic counseling is strongly advised for all persons with thalassemia. Two parents,
each with beta thalassemia trait, have a one in four chance of conceiving a child with beta thalassemia
major and a three in four chance the child will have thalassemia trait or be normal
Chorionic villus sampling using polymerase chain reaction technology to detect point mutations or
deletions can identify infants affected with beta thalassemia
Beta thalassemia major or intermedia is a chronic disease with a signifcant impact on the patient and
the patient's family and offspring. Education about the genetics of the disease, prenatal diagnosis
options, and psychological therapy to help manage the complications is appropriate.
Persons with thalassemia trait have a normal life expectancy. Persons with beta thalassemia major live
an average of 17 years and usually die by 30 years of age. Most deaths are caused by the cardiac
complications of iron overload.
KEY FOT THALASSEMIA:
1. Physical signs are due to low hemoglobin and low oxygen carrying capacity of red blood cells.
2. Boy is short statured because of malnutrition because of chronic illness and have prominent
facial and frontal bones because of extramedullary hematopoesis.
3. Spleen is enlarged because of splenic sequestration of abnormal RBCs and extramedullary
hematopoesis.
4. Blood reports shows microcytic hypochromic anemia with reticulocytosis.
5. due to intramedullary hemolysis(ineffective erythropoesis) and intracorpuscular hemolysis.
6.Most likely diagnosis is thalassemia major.
7. Iron deficiency anemia and anemia of chronic disease.
8. In anemia of chronic diseases MCV and MCHC are normal or low and reticulocyte count is not
increased. While in iron deficiency anemia both MCV and MCHC are low with low reticulocyte
count.
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9. Patients of thalassemia are asymptomatic at birth because main hemoglobin at that time is
HBF which in such patient is normal.
10. Thalassemia major is an autosomally inherited recessive disease, which occur in children of
parents who both have thalassemia trait, chances of which are highly increased in case of
interfamily marriages.
11. Preconception genetic councelling and in pregnant ladies chorionic villous sampling using
polymerase chain reaction technology to detect point mutation or deletions in the genes.
12. Autosomal recessive inheritance.
13. Fetal hemoglobin (HBF) has two alpha and two gamma chains in contrast to adult
hemoglobin
(HBA) which has two alpha and two beta chains.
14.Avoid interfamily marriages if history of disease is present or suspected of disease .
Ref. guytan Physiology 11- edition.
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Module III: BLOOD AND IMMUNITY
WEEK 3
By the end of the third week of module III, student will be able to correlate cellular
events and chemical mediations in acute and chronic inflammation with clinical presentations.
Relate structure and formation of antibodies with their functions and to relate histology of
spleen, lymph node and bone marrow with their normal and abnormal functions.
LEARNING OBJECTIVES:

Differentiate between cells of the immune system on the basis of their structure and
function

Differentiate between cellular and humoral immunity and their respective functions/
actions

Differentiate between acute and chronic inflammation
Case Presentation
A 40-year old professional lady had been experiencing generalized
weakness and fatigability for the last one week. She noticed small red spots
scattered all over her skin and bleeding from her gums since a day prior to
coming to her physician. She does not have a history of taking any
medications nor fever or flu like illness.
On examination the physician found her to be pale with petechiae
distributed all over body and also she was bleeding from the gums. The
initial laboratory workup revealed
Table 1. complete blood count
Hemoglobin (Hb)
10.2 g/dl
WBC
8000/cmm
Platelet count
23,000/cumm
Bleeding time
More than 10 minutes
Clotting time
5 minutes
Prothrombin time
15/13
9
Activated partial
thromboplastin
time
35/35
Questions
1.
2.
3.
4.
5.
6.
7.
How would you explain general weakness and fatiguability in this lady?
Describe the mechanism of formation of red spots and bleeding?
What abnormalities are seen in this CBC report?
How do you interpret the full blood count and coagulation screen?
What advice should be given to the patient?
What if clotting time is prolonged in a patient?
How is the blood coagulation cascade affected if a patient has prolonged APTT
and normal PT?
8. Define thrombocytopenia and enlist the common causes of this condition.
9. What are the most dreadful consequences of thrombocytopenia?
10. At what platelet level is there a danger of spontaneous intracranial bleeding?
11. Discuss the role of spleen in the maintenance of platelet count?
12. Why is someone more likely to bleed to death when an artery is cleanly severed
than when it is crushed and torn?
13. How can liver dysfunction causes bleeding disorders?
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Facilitator’s Guide:
Immune Thrombocytopenic Purpura
Immune thrombocytopenic purpura (ITP) is a clinical syndrome in which a decreased
number of circulating platelets (thrombocytopenia) manifests as a bleeding tendency,
easy bruising (purpura), or extravasation of blood from capillaries into skin and mucous
membranes (petechiae).
Pathophysiology
In immune thrombocytopenic purpura (ITP), an abnormal autoantibody, usually
immunoglobulin G (IgG) with specificity for 1 or more platelet membrane glycoproteins
(GPs), binds to circulating platelet membranes.
Autoantibody-coated platelets induce Fc receptor-mediated phagocytosis by
mononuclear macrophages, primarily but not exclusively in the spleen.The spleen is the
key organ in the pathophysiology of immune thrombocytopenic purpura (ITP), not only
because platelet autoantibodies are formed in the white pulp, but also because
mononuclear macrophages in the red pulp destroy immunoglobulin-coated platelets.


If bone marrow megakaryocytes cannot increase production and maintain a
normal number of circulating platelets, thrombocytopenia and purpura develop.
Impaired thrombopoiesis is attributed to failure of a compensatory increase in
thrombopoietin and megakaryocyte apoptosis.
Autoantibody specificity
o In persons with chronic immune thrombocytopenic purpura (ITP),
approximately 75% of autoantibodies are directed against platelet
GPIIb/IIIa or GPIb/IX GP complexes.
o Presumably, the remaining 25% are directed against other membrane
epitopes, including GPV, GPIa/IIa, or GPIV.

Role of the spleen
o The spleen is the site of autoantibody production (white pulp).
o It is also the site of phagocytosis of autoantibody-coated platelets (red
pulp).
o The slow passage of platelets through splenic sinusoids with a high local
concentration of antibodies and Fc-gamma receptors on splenic
macrophages lend to the uniqueness of the spleen as a site of platelet
destruction.
o Low-affinity macrophage receptors, Fc gamma RIIA, and Fc gamma RIIIA
bind immune-complexed IgG and are the key mediators of platelet
clearance.

Platelet destruction
o The mononuclear macrophage system of the spleen is responsible for
removing platelets in immune thrombocytopenic purpura (ITP), because
splenectomy results in prompt restoration of normal platelet counts in
most patients with immune thrombocytopenic purpura (ITP).
o Platelets are sequestered and destroyed by mononuclear macrophages,
which are neither reticular nor endothelial in origin. Therefore, the former
designation of reticuloendothelial system is considered imprecise.
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o
Immune destruction of immunoglobulin-coated platelets is mediated by
macrophage IgG Fc (Fc gamma RI, Fc gamma RII, and Fc gamma RIII)
and complement receptors (CR1, CR3).

Hemorrhage: The primary cause of long-term morbidity and mortality in patients
with immune thrombocytopenic purpura (ITP) is hemorrhage. If platelet counts
are less than 50 X 109/L (<50 X 103/µL) bleeding after trauma an surgical
procedures is massive and spontaneous bleeding occurs when platelets drops to
less than 20 X 109/L (<20 X 103/µL)

Intracranial hemorrhage: The most frequent cause of death in association with
immune thrombocytopenic purpura (ITP) is spontaneous or accidental traumainduced intracranial bleeding. Most cases of intracranial hemorrhage occur in
patients whose platelet counts are less than 10 X 109/L (<10 X 103/µL).

Children may be affected at any age with immune thrombocytopenic purpura
(ITP), but the prevalence peaks in children aged 1-6 years.

Adults may be affected at any age, but most cases are diagnosed in women
aged 30-40 years.

Thrombocytopenia is a recognized complication after infection with Epstein-Barr
virus, varicella virus, cytomegalovirus, rubella virus, or hepatitis virus (A, B, or C)
helicobacter pylori gastritis and various drugs



Physical
Anemia
Widespread petechiae and ecchymoses, oozing from a venipuncture site,
gingival bleeding, and hemorrhagic bullae indicate that the patient is at risk for a
serious bleeding complication. If the patient's blood pressure was taken recently,
petechiae may be observed under and distal to the area where the cuff was
placed and inflated.
Splenomegaly excludes the diagnosis of immune thrombocytopenic purpura
(ITP).

Workup
Laboratory Studies
 Determination of complete blood cell (CBC) count
o The hallmark of immune thrombocytopenic purpura (ITP) is isolated
thrombocytopenia.
o Anemia and/or neutropenia may indicate other diseases.

Peripheral blood smear
o The morphology of red blood cells (RBCs) and leukocytes is normal.
o The morphology of platelets is typically normal, with varying numbers of
large platelets. Some persons with acute immune thrombocytopenic
purpura (ITP) may have megathrombocytes or stress platelets, reflecting
the early release of megakaryocytic fragments into the circulation.

Test for antiplatelet antibodies may be helpful in the diagnosis
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

Direct antiglobulin test: If anemia and thrombocytopenia are present, a positive
direct antiglobulin (Coombs) test result may help establish a diagnosis of Evans
syndrome.
Bone marrow aspirate
The cellularity of the aspirate and the morphology of erythroid and myeloid
precursors should be normal. The number of megakaryocytes may be increased.
Because the peripheral destruction of platelets is increased, megakaryocytes may be
large and immature, although in many cases the megakaryocyte morphology is
normal.
The goal of medical care is to increase the platelet count to a safe level, permitting
patients with immune thrombocytopenic purpura (ITP) to live normal lives while
awaiting spontaneous or treatment-induced remission. Immune thrombocytopenic
purpura (ITP) has no cure, and relapses may occur years after seemingly successful
medical or surgical management.

Corticosteroids (ie, oral prednisone, IV methylprednisolone) for the initial
management of immune thrombocytopenic purpura (ITP).
o IV immunoglobulin (IVIG) is the alternative treatment, but it is expensive.

Among the treatment options after corticosteroids, IVIG are immuno suppressive
agent
o Splenectomy is the treatment when conservative management fails.
Media file 1: Peripheral blood smear from a patient with immune thrombocytopenic purpura (ITP) illustrates a decreased number of
platelets, a normal-appearing neutrophil, and erythrocytes. ITP is diagnosed by excluding other diseases; therefore, the absence of other
findings from the peripheral smear is at least as important as the findings are observed. This smear demonstrates the absence of immature
leukocytes (as in leukemia) and fragmented erythrocytes (as in thrombotic thrombocytopenic purpura) and no clumps of platelets (as in
pseudothrombocytopenia).
1. Stasi R, Evangelista ML, Stipa E, et al. Idiopathic thrombocytopenic purpura: current concepts in pathophysiology and
management. Thromb Haemost. Jan 2008;99(1):4-13
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