Haemolytic anaemias types and causes-1.pdf

Haemolytic anaemias (HAs)
• HAs are defined as those anaemias
which result from an increase in the
rate of red cell destruction.

• Because of erythropoietic hyperplasia
and anatomical extension of bone
marrow, red cell destruction may be
increased several fold before the
patient become anaemic ---
compensated haemolytic anaemia.
• The normal adult marrow, after full
expansion, is able to produce red cells
at 6-8 times the normal rate.

Classification of HA
• The HA can be classified in several different
ways:
1- Site of haemolysis:
• Extravascular haemolytic disorders -
macrophages of the RES
• Intravascular haemolytic disorders- within the
circulatory system
• In many of the cases there is a combination of
both extra and intravascular haemolysis.

Extravascular haemolysis
• Red cell destruction
usually occurs in the
cell of the RES.

Intravascular haemolysis
• Destruction of red
cells occur inside the
blood vessels.

Cont….
2- Site of defect:
• Intrinsic defect (intracorpuscular)-
structural or functional defect within the
red cell.
• Extrinsic defect (extracorpuscular)- an
abnormality in the red cell environment.

Cont…
3- Inherited or acquired:
• Inherited HA are usually caused by intrinsic
defect.
• While acquired HA are caused by an extrinsic
defect.
• However there are some exceptions:
Paroxysmal nocturnal haemoglobinuria (PNH)
which is an acquired intrinsic defect, and
severe hereditary G6PD enz deficiency which
requires the presence of an extrinsic trigger
such as the antimalarial drug for the intrinsic
defect to manifest.

Inherited & acquired HA
Hereditary HA
• Membrane defects e.g
hereditary spherocytosis
• Metabolic defect e.g
G6PD deficiency.
• Haemoglobin defects
e.g sickle cell disease.
Acquired HA
– Immune
-Autoimmune eg AIHA
-Alloimmune e.g HDN,
HTR
– Red cell
fragmentation
syndromes
– March
haemoglobinuria
– Infections
– Chemical and physical
agents.
– PNH

Approach to the diagnosis of
haemolytic anaemias.

Patient’s history
• Good history is essential to provide guidance for
the diagnosis of haemolytic disorders. The
following points should not be neglected:
• Family history--- hereditary conditions, mode of
inheritance.
• Ethnic origin--- G6PD deficiency is most
common in Mediterranean and Chinese
populations.
• Past history--- Neonatal jaundice may be
indicative of congenital conditions as HS or
G6PD deficiency.
• Triggering events--- history of drugs, infections

Clinical features
• Pallor of the mucous membranes
• Mild fluctuating jaundice
• Splenomegaly
• Dark urine
• Pigment gall stones.
• Ulcers around the ankle
• Aplastic crisis may complicate viral infections.
• Growth retardation
• Hypertrophic skeletal changes

• Leg ulcers in
patients with severe
congenital
haemolytic
disorders. e.g sickle
cell anaemia

• Skeletal changes in
patients with b
thalassaemia.

Laboratory findings
• The lab. Findings are divided into 3
groups:
1- Features of increased red cell
breakdown.
2- Features of increased red cell
production.
3- Damaged red cells.

Laboratory findings
1-Features of increased red cell
breakdown:
• Raised S.bilirubin, unconjugated and
bound to albumin.
• Increased urine urobilinogen.
• Increased faecal stercobilinogen.
• Absent S.haptoglobins (saturated with
Hb and removed by the RE cells).

Laboratory findings
2-Features of increased red cell
production:
• Reticulocytosis
• Bone marrow erythroid hyperplasia.

Laboratory findings
• 3-Damaged red cells:
• Morphology– microspherocytes,
elliptocytes, fragments, etc.,….
• Special tests: Osmotic fragility,
autohaemolysis…..
• Red cell survival is shortened; this is
best shown by 51Cr labelling with study
of the sites of destruction.

• Reticulocytosis is a
feature of increased
red cell production.
• New methylene blue
is used to stain the
reticulocytes

• Fragmented cells,
and bitten cells are
sings of damaged
cells occurring in
haemolysis

Intravascular haemolysis
• Free Hb will be released from damaged red
cells.
• This free Hb will rapidly saturates plasma
haptoglobins. The complex will be removed
by the liver.
• The excess free Hb is filtered by the
glomerulus, and free Hb will enter the urine,
as iron is released, the renal tubules become
loaded with haemosiderin.
• Methaemalbumin and haemopexin are also
found in the process of IV haemolysis.

• The process of
intravascular
haemolysis
• Liberation of free Hb
• Filtered through the
kidney
• Appear in urine as
haemoglobinuria

Lab features of intravascular
haemolysis
• Haemoglobinaemia & haemoglobinuria.
• Haemosiderinuria (iron storage protein
in the spun deposit of urine).
• Methaemalbumin (detected by
Schumm‟s test).

Haemoglobinuria
• Notice the dark
colour of urine
compared to the
normal colour in the
other container.
• This is a sign of
intravascular
haemolysis.

Conclusion
• Good history taking is essential in guiding the
physician towards the correct diagnosis.
• Clinical findings seldom are sufficient to
enable a definitive diagnosis of a particular
haemolytic condition to be made.
• Lab investigations play a central role in the
accurate diagnosis of haemolysis.

Hereditary haemolytic anaemias
• Membrane defects – congenital
spherocytosis
• Metabolic defects – G6PD enzyme
deficiency
• Haemoglobin defects
– Qualitative defects – sickle cell anaemia
– Quantitative defects – Thalassaemia

The clinical phenotypes of hereditary
membrane disorders
The mutations affecting the red cell
membrane are many, but the effect on the
phenotype can be classified into 5 main
categories.
• Hereditary spherocytosis
• Hereditary elliptocytosis and Hereditary
pyropoikilocytosis
• South-East Asian ovalocytosis
• Hereditary acanthocytosis
• Hereditary stomatocytosis

Hereditary spherocytosis (HS)
• It is the most common hereditary
haemolytic anaemia in North
Europeans.
• The prevalence is 200-300 per million in
the population (European population).

Pathogenesis of HS
• It is caused by a defect in the proteins
involved in the interactions between the
membrane cytoskeleton and the lipid bilayer
of the red cell.
• About 60% of HS cases result from a defect
in the ankyrin-spctrin complex.
• A further 25% involve deficiency in band 3,
the anion channel.
• In the remainder, there is a deficiency of
protein 4.2 or no abnormality detected.

Clinical features
• The inheritance is autosomal dominant.
• Rarely it may be autosomal recessive.
• The anaemia may present at any age from
infancy to old age.
• Jaundice is fluctuating.
• HS is also called “familial acholuric jaundice”
emphasizing the presence of jaundice in
absence of bile in urine.
• Splenomegaly occurs in most of the patients.
• Pigment gall stones are frequent.

Haematological findings in HS
• Features of extravascular haemolysis
are present.
• Anaemia is usual.
• Reticulocytosis 5-20%
• Microspherocytes are seen in the blood
film. (densely staining with smaller
diameters than normal red cells).

Other investigations
• The classic finding is that the osmotic
fragility is increased in HS with a shift of
the curve to the right.
• Autohaemolysis is increased and
corrected by glucose.
• Direct antiglobulin test (Coombs test) is
normal.

Autohaemolysis test in HS
There is increased
haemolysis in the
patient in
comparison with the
control. Glucose has
given partial
correction.

Treatment
• Patients with well-compensated haemolysis
and no transfusion requirements need no
treatment other than reassurance and folic
acid supplements.
• The principal form of treatment is
splenectomy although this should not be
performed unless clinically indicated because
of the risk of post-splenectomy sepsis,
particularly in early childhood.

Hereditary elliptocytosis (HE)
• HE is inherited as an autosomal-dominant
trait except for a rare Melanesian type that
inherited as a recessive trait. The disorder
occurs in all racial groups with an occurrence
of .02% to 0.05%.
• The disease is heterogeneous in the degree
of haemolysis and clinical severity. The
prominent peripheral blood finding is an
increase in oval and elongated cells
(elliptocytes).

Pathophysiology
• The principal defect involves horizontal
membrane interactions.
1) Decreased association of Spectrin dimmers
to form tetramers due to defective spectrin
chains.
2) Deficiency or defective in band 4.1 which
aids in binding spectrin to actin.
3) Defective association of spectrin –
ankyrin due to spectrin chains
mutants.

Pathophysiology
• Each of these defects can lead to skeletal
disruptions that can cause the cell to become
elliptical in shape and/or fragment under the
stresses of circulation depending on the extent of
the defect.
• Mildly dysfunction proteins cause only
elliptocytosis ; whereas, severely dysfunctional
proteins cause membrane fragmentation in
addition to elliptocytosis.

Pathophysiology
• Elliptocytosis with membrane fragmentation causes
decrease in cell surface area and reduced cells
deformability.
• The lifespan of these cells is severely shortened.
• HE erythrocytes are abnormally permeable to Na+.
• This altered permeability demands an increase in
ATP to maintain osmotic equilibrium.
• In the spleen the cell quickly deplete their ATP and
become osmotically fragile.

Clinical finding
• Ninety percent of patients with HE show no
signs of haemolysis.
• Patients have compensated haemolytic
disease.
• Anaemia is not characteristic.

Lab- finding
• The most consistent and characteristic lab finding in all
variants is prominent elliptocytosis. Haemoglobin levels are
usually greater than 12 g/l.
• Reticulocytes are mildly elevated to 4%.
• In HE variant haemoglobin is 9 to 10 g/dl, and reticulocyte
are elevated to 20%.
• Microelliptocyte, schistocytes, and spherocytes are usually
evidence.
• Bone marrow show erythroid hyperplasia with normal
maturation.

Hereditary stomatocytosis
• It is a rare autosomal-dominant haemolytic
anaemia in which the erythrocyte membrane is
abnormally permeable to both Na+ and K+.
• As a result, the intracellular concentration of
cations increases, water inters the cell, and the
overhydrated cells take on the appearance of
stomatocytes.
• Stomatocytes on dried stained blood films are
erythrocytes with a slit-like (mouth-like) area of
pallor.

Pathophysiology
• The stomatocytes cells are osmotically
fragile and less deformable than normal
cells and as a result the cells are
sequestered in the spleen and
phagocytosed.

Lab. Finding
• Anemia is usually mild (8 to 10 g/dl).
• Bilirubin is increased.
• Reticulocytosis is moderate.
• The blood film is remarkable for 10 to
50% stomatocytes.
• Osmotic fragility and autohaemolysis
are increased.
• Autohaemolysis is partially corrected
with glucose and ATP.

Lab. finding
• Inherited stomatocytosis must be
differentiated from acquired causes of
stomatocytosis.
• Stomatocytosis also are seen in an
acquired defect in acute alcoholism, liver
disease, and cardiovascular disease.
• In these acquired conditions there is no
cation leaks, and little haemolysis is
present.

South-East Asian ovalocytosis
• This is common in Malaysia, Indonesia
and the Philippines.
• It is due to Band 3 protein abnormality.
• The cells are rigid and resist invasion by
malaria parasite.
• Most cases are asymptomatic.

Blood film in hereditary stomato-
ovalocytosis
• basophilic stippling
and numerous
stomatocytes.

Defective red cell metabolism
G6PD enzyme deficiency
Pyruvate kinase deficiency

• G6PD functions to
reduce nicotinamide
adenine dinucleotide
phosphate (NADPH)
while oxidizing
glucose-6-
phosphate.
• NADPH is needed for
the production of
reduced glutathione
(GSH) which is
important to defend
the red cells against
oxidant stress.

G6PD deficiency
• More than 400 variants due to point
mutations or deletions of the enzyme G6PD
have been characterized which show less
activity than normal.
• Worldwide over 400 million people are G6PD
deficient in enzyme activity.

Clinical features
There are four main syndromes associated
with G6PD enzyme deficiency.
• Neonatal jaundice (class I,II,III)
• Favism (class II)
• Chronic non spherocytic haemolytic anaemia
(CNSHA) (class I)
• Drug induced haemolytic anaemia (class III)

G6PD deficiency
• The inheritance is sex-linked, affecting
males, and carried by females.
• The main races affected are in West
Africa, the Mediteranean, the Middle
East, and South East Asia.

Lab Diagnosis
• Between crises blood count is normal.
• The enzyme deficiency is detected by
– One of a number of screening tests or
– By direct enzyme assay on red cells.
• During the crisis, the blood film may show
contracted and fragmented cells, bite and
blister cells.
• Enzyme assay may give a false normal level
in the phase of acute haemolysis.
• There are features of intravascular
haemolysis.

G6PD deficiency
• The blood film shows
irregularly contracted
cells [deep red arrows]
and sometimes
hemighosts [deep blue
arrow] in which all the
haemoglobin appears to
have retracted to one
side of the erythrocyte.

Management
• Education in the avoidance of oxidising
substances is important
• The offending drug is stopped.
• Any underlying infection is treated.
• High fluid intake is encouraged to avoid
renal failure.
• Blood transfusion, if necessary, for
severe anaemia.

Pyruvate kinase deficiency
Deficiency of glycolytic enzymes
• Most common after G6PD def
– Deficient ATP production, chronic haemolytic anemia
• Autosomal recessive - Rare [prevalence 1/10,000]
Clinical features
• Most are jaundice and anemic infancy and childhood
• Occasional mild diagnosed only in adulthood
• Hydrops fetalis
• Compensated haemolytic anemia
• Neonatal jaundice
• Gallstone
• Frontal bossing

Lab finding
• Severity of anaemia varies widley (4 – 10
g/dl).
• P. Smear: poikilocytosis prikle cells contracted
RBCs with spicules.
• Direct enzyme assay (decreased enzyme
activity)
• Rise of intracellular 2,3-DPG (reduce severity)
• Autohaolysis increased not corrected by
glucose as in HS.

Defective haemoglobin
(Haemoglobinopathies)

Haemoglobinopathies:
•Sickle cell anaemia.
•Thalassaemias.
•Haemoglobin C disease.
•Haemoglobin S/C disease.
•Haemoglobin D (Punjab, Los Angelos).
•Haemoglobin E.
•Unstable haemoglobin.

Defective haemoglobin
Sickle cell anaemia
• It is group of haematological disorders results
from single base change in the DNA coding for
the amino acid in the sixth position in the b-
globin chain. This leads to an amino acid
change from glutamic acid to valine  HbS
will be formed instead of the normal Hb.

Sickle cell anaemia
• Hb S is insoluble and forms crystals when
exposed to low oxygen tension.
• Deoxygenated sickle Hb polymerizes into long
fibrils.
• The red cells sickle and may block the
different areas of the microcirculation or large
vessels causing infarcts of various organs.
• It is widespread in West Africa.

Classification
• Sickle cell trait (heterozygote).
• Sickle cell disease (homozygote).

Pathophysiology of sickle cell disease

Clinical finding in sickle cell disease
• Vaso-occlusitve crisis lead to infarction in several
organs such as bones, lung, spleen and brain.
• Visceral sequestration crises eg. Sickle chest
syndrome.
• Aplastic crises due to infection or folate def. sudden
fall in Hb.
• Haemolytic crises increase rate of haemolysis with
fall in Hb and accompany by painful crises.
• Leg ulcer.
• Leg hand syndrome.
• Spleen enlargement.

Laboratory findings
• Hb is usually 6-9 g/dl.
• Sickle cells and target cells occur in the blood.
• Screening tests for sickling are positive.
• Hb electrophoresis in Hb SS, no Hb A is
detected. The amount of Hb F is variable 5-
15%.

Sickle
Cells
Erythroblasts
Howell-
Jolly Body
Sickle Cell Anemia – blood film

Sickle cell trait
• Sickle cell trait is heterozygous βs state
(HbAS).
• The patient has one normal β-gene and one
abnormal βs –gene .
• Hb A constitute more than 50% of total Hb
in these individuals so there is no clinical
symptoms .
• Complication of splenic infarction is possible if
the affected individuals exposed to prolong
hypoxia.

Other Sickling Disorders
Other types of Hb combine with sickle Hb
2. Hemoglobin S-C disease
– Sickle haemoglobin (HbS) + (HbC)
3. Hemoglobin S-Beta thalassemia
– Beta thalassaemia gene reduces the
amount of HbA that can be made
– Sickle haemoglobin (HbS) + reduced HbA
– Milder form of Sickle Cell Disorder than
sickle cell anemia

Definition
• Thalassaemias are heterogeneous group
of genetic disorders due to mutation that
causes decrease in the rate of synthesis
of one of the constituent globins chains
,usually α or β chain of haemoglobin.

Types of thalassaemias
1. α-Thalassaemia (α-globin chain is impaired)
2. β-Thalassaemia (β-globin chain is impaired).
3. δ-Thalassaemia (δ-globin chain is impaired).

β-Thalassaemia
• β-Thalassaemia is a result of several different
molecular defect.
• Over 100 mutations have been described that
result in partial to complete absence of β-gene
expression.
• β- Thalassaemia rarely can be due to deletion
of structural gene.

β-Thalassaemia
• Mutation may affect any step in the pathway of
globin gene expression including gene
transcription, RNA processing of m-RNA
translation, and post-translation integrity of the
protein.
• Two types of abnormal genes (βthal )are
designed β0 and β+).

Classification of β- Thalassaemia
• Previously, thalassaemia were commonly
classified according to clinical severity of the
disease into:
-Thalassaemia major (Cooley's anaemia)
-Thalassaemia intermedia
- Thalassaeia minor

Classification of β-Thalassaemia
• Genotypic classification into:
• Homozygous β- Thalassaemia (β0 β0 , β+ β+).
• Heterozygous (β β0 or β β+, β0 β+).

Classification & Terminology
β-Thalassemia
• Normal b/b
• Minor b/b0
b/b+
• Intermedia b0/b+
• Major b0/b0
b+/b+

Pathophysiology
• Normally equal quantities of α- and β- are
synthesized by maturing erythrocyte.
• IN β-Thalassaemia, synthesis of β- chains
is deceased or absent, resulting in an
excess of free alpha chains.

Pathophysiology
• This imbalance synthesis of Beta and alpha
has several effects:
1. Decrease in total erythrocyte haemoglobin
production
2. Ineffective erythropoiesis
3. Chronic haemolytic process

Homozygous β-Thalassaemia
• This disorder is caused by marked reduction or
absence of β- chains.
• Clinical finding:
1- The general signs of anaemia.
2- Heart failure
3- Growth retardation and skin pigmentation.
4- gout and gallstone
5- spleenomegally
6- bone changes and bossing of the skull
7- Iron over load develop due to repeated transfusion

Laboratory diagnosis
• Hb may be low as 2 to 3 g/dl.
• MCV,MCH,MCHC are also markedly deceased.
• The cord blood normally has 20% of Hb A.
• The cord blood of infant with Thalassaemia has
less than 2% Hb A.
• Peripheral blood picture shows anisocytosis,
poikelocytosis, schistocytes, nucleated red cells,
target cells, polychromasia.

Laboratory diagnosis
- Haemoglobin electrophoresis show absence of
Hb A increase in Hb A2 and Hb F (90%) is
characteristic of β0 β0 .
- The other homozygous β+ β+, show HbA (24%
to 36 %).

Haemoglobin analysis by Hb
electrophoresis
Types of Haemoglobin:
• HbA:a2b2
• Hb A2: a2d2
• HbF:a2g2
• Embryonic Hb: Portland z2g2
• Hb Bart’s: g4
• Hb H: b4

Partial or lack of HbA synthesis ↓MCHC &
MCH Hypochromia & microcytosis
Normal
Thalassaemia

Reticulocytes undergo intramedullary death
Inadequate production + ineffective erythropoiesis
+ haemolysis Anaemia

↑Haemolysis ↑demands of phagocytic function
 hyperplasia of phagocytes
Hepatosplenomegaly
To compensate anaemia extramedullary
haemopoiesis in liver, spleen & brain
Organomegaly

↑Erythropoiesis marrow expansion & thinning
of cortex of skull bone Thalassaemia facies

Heterozygous β- Thalassaemia
The heterozygous state of β- Thalassaemia
(Thalassaemia minor) results from the inheritance
of either β+ or βo Thalassaemia gene and one
normal β-gene is present. The normal gene directs
the synthesis of β-gene and the erythrocyte survival
is nearly normal.

The heterozygote disorder appears
symptomless except in periods of stress and
pregnancy when moderate microcytic anaemia
develops.

•The anaemia is mild with Hb 9 to 11 mg/dl
•The RBCs is double for what expected at that Hb
con.
•The cord blood of infant has 6 % to 10% HbA
•The cells are microcytic (MCV 55 to70 fl)
•The peripheral blood smear shows variable
Anisocytosis and poikelocytosis target cells and
basophilic stippling.
Lab. Diagnosis

Bone marrow shows erythroid hyperplasia and
normoblast poorly filled with haemoglobin.
* Haemoglobin electrophoresis demonstrate Hb
A2 from 5 to 7% with a mean of 5.5.
* Hb F may be normal or increased.
* The blood picture is similar to that of iron
deficiency anaemia.

α-Thassaemia
An absence or deficiency of α-chain synthesis due
to deletion of α-genes.

In normal individual HbA, HbA2 and HbF need α-
chain for their formation.
4 genes of α-chain, each pair on short arm of
chromosome 16 present with genotype α,α/α,α.
In α-thalassaemia, deletion of α-genes reduction
or absence of synthesis of α-chain depending on
number of α-gene deletion.
Pathogenesis of α-Thalassaemia

• ↓α-chain synthesis free γ-chain in the
fetus & β-chain in infant of 6 months, and
continue in the rest of life.
• Complementary 4γ and 4β are aggregated
 Hb Bart (4γ ) and HbH (4β ),
respectively.

Variants of α-Thalassaemia
• Silent carrier
– Deletion of single α-gene
– Genotype α/αα
– Asymptomatic
– Absence of RBC abnormality
• Thalasaemia trait
– Deletion of 2 α-genes
– Genotype --/αα
– Asymptomatic, minimal or no anaemia
– Minimal RBC abnormalities

• Hb H disease
– Deletion of 3 α-genes
– Genotype --/- α
– 75% reduction of α-chain
– 25% α-chain synthesis small amount of HbF, HbA,
& HbA2
– Fetus can survive
– Severe anaemia
– Severe RBC abnormalities
• Hydrops fetalis
– Deletion of all α-genes
– Genotype --/--
– Absence of α-chain synthesis
– Only Hb Bart (γ4) is produced (High affinity for O2
and can not dissociate O2 to tissue)

High oxygen affinity-hypoxia instability of homotetramers inclusion
bodies. Membrane damage shortened red cell survival - haemolysis
spleenomegaly – hypersplenism.
The pathophysiology of α thalassaemia

Hb H
• Hb H is an unstable , thermolabile protein with
an oxygen affinity 10 times that of Hb A.
• Because is an unstable Hb it precipitate chronic
haemolytic process.
• Hb H is particularly sensitive to oxidation,
forming intracellular precipitate in older cells.
• The life span shortened as these inclusions
injure the cell membrane.

Terminology
a+ one gene on one chromosome is
inactivated.
a0 both genes on one chromosome are
inactivated.

The genetics of α-thalassaemia

α-Thalassaemia: hydrops fetalis

• α-Thalassaemia: haemoglobin H disease (three α-globin
gene deletion). The blood film shows marked hypochromic,
microcytic cells with target cells and poikilocytosis

Acquired haemolytic anaemias
Immune haemolytic anaemias
Non-immune haemolytic anaemias

Classification of acquired HA
Acquired HA
– Immune
-Autoimmune eg AIHA
-Alloimmune e.g HDN, HTR
-drug induced immune HA e.g methyl dopa
– Red cell fragmentation syndromes
– March haemoglobinuria
– Infections
– Chemical and physical agents.
– PNH

Immune HA
Autoimmune HA ( AIHA)
• These are caused by antibody
production by the body itself against its
own red cells.
• It is divided into warm and cold types
according to whether the antibody
reacts more strongly with red cells at
37O C or 4O C.

AIHA classification
Warm type
• Idiopathic
• Secondary
• SLE, other
autoimmune
diseases
• CLL, lymphomas
• Drugs
Cold type
• Idiopathic
• Secondary
• Infections-
Mycoplasma
pneumonia,
Infectious
mononucleosis.
• Lymphoma
• Paroxysmal cold
haemoglobinuria.

Laboratory findings in warm AIHA
• Haematological and biochemical
findings of extravascular haemolysis
with spherocytosis prominent in the
peripheral blood.
• Direct antiglobulin test is positive
(Coombs test) as a result of IgG, IgG
and complement or IgA on the cells.

Warm AIHA
• anaemia, spherocytes
and polychromatic
macrocytes. The
blood film in this
condition occasionally
shows small red cell
agglutinates.

Cold AIHA
• The antibody attaches to red cells mainly in
the peripheral circulation where the blood
temperature is cooled.
• The AB is usually IgM and binds to red cells
at 4o C.
• IgM antibodies are highly efficient in fixing
complement.
• Both intravascular and extravascular
haemolysis can occur.

Laboratory findings in cold AIHA
• Similar to those of warm AIHA, except
that spherocytosis is less marked.
• Red cells agglutinate in the cold.
• DAT reveals complement (C3d) only on
the red cell surface.( the AB having
eluted off the cells in warmer parts of
the circulation).

Cold agglutinins
• very large red cell
agglutinates form on
spreading the blood film and
and an abnormality can be
appreciated on
macroscopic inspection of the
blood film.
The nature of the abnormality
can be confirmed by
microscopic examination. If
the blood is warmed before
spreading, the degree of
abnormality is much less.

Cold AIHA
• Red cell clumping in
cold AIHA

Alloimmune HA
• In these anaemias, antibody produced
by one individual reacts with red cells of
another.
• Two important conditions
– Transfusion of ABO incompatible blood
– Rhesus disease of the newborn

Rh-HDN
• Blood film in rhesus
haemolytic disease
of the newborn
showing several
spherocytes.

Non immune HA
Red cell fragmentation syndromes
• They arise through physical damage to
red cells on abnormal surfaces.
– Artificial heart valves or arterial grafts.
– Malignant hypertension
– Haemolytic uraemic syndrome…….

Mechanical HA (red cell fragmentation
syndrome)
• There are
macrocytes
and red cell
fragments.

Non immune HA
Infections
• Malaria causes haemolysis by
extravascular destruction of parasitised
red cells as well as intravascular
haemolysis accompanied by acute renal
failure caused by Falciparum malaria.
• Clostridium perfringens  intravascular
haemolysis.

P.vivax
• Blood film in P. vivax
malaria.World-wide,
malaria is a very
common cause of
haemolytic anaemia.

Blood film in P. falciparum malaria
a very heavy
parasitaemia with
numerous ring forms
and one early
gametocyte. World-
wide,malaria is a very
common cause of
haemolytic anaemia. P.
falciparum can cause
acute intravascular
haemolysis leading to
'blackwater fever'.

Clostridium perfringens sepsis
• . The blood film shows
severe anaemia and
marked spherocytosis.
The spherocytosis is
consequent on direct
damage to the red cell
membrane by a
bacterial toxin.

Non-immune HA
Chemical and physical agents
- Certain drugs as dapsone and
salazopyrine can cause oxidative
intravascular haemolysis.
- Severe burns damage red cells causing
spherocytosis or acanthocytosis.

Burns
• spherocytes and
microspherocytes..
There may also be a
'packed film'
consequent on elevation
of the Hb as a result of
loss of plasma into
burnt tissues. A film as
abnormal as this is
usually associated with
burns that are so severe
that they are fatal.

Non-immune HA
Paroxysmal nocturnal haemoglobinuria
(PNH)
• This is a rare, acquired, clonal disorder
• The red cells are sensitive to lysis by
complement and the result is chronic
intravascular haemolysis.

Pathophysiology of PNH
• PNH is a rare, acquired disorder of marrow
stem cells in which there is deficient
synthesis of the glycosylphosphatidyl inositol
(GPI) anchor,(a structure that attaches
several surface proteins to the cell
membrane).

Cont…
• It results from mutations in the X chromosome
gene coding for phosphatidyl inositol glycan
protein A (PIG-A) which is essential for the
formation of the GPI anchor.
• GPI-linked proteins (such as CD55 and CD59)
are absent from the abnormal stem cell surface
of all the cells.

Cont…
• These proteins, CD59 or membrane inhibitor of
reactive lysis (MIRL) and CD55 or decay
accelerating factor (DAF), protects the red cell
from being lysed by the membrane attack complex
(C5–C8) that forms when complement (C) is
activated and the result is chronic intravascular
haemolysis.

Cont…
• Chronic intravascular haemolysis in PNH is
probably explained by activation of C through
the „alternative‟ pathway
• CD55 and CD59 are also present on white cells
and platelets.
• In addition to haemolytic anaemia, the patient
may have thrombosis and pancytopenia.

Clinical features
1. Haemoglobinuria due to intravascular haemolysis
2. Haemolytic anaemia with a low platelet and/or
low neutrophil count
3. Haemolytic anaemia and recurrent abdominal
pain with or without blood in the stool.
4. Hepatic vein thrombosis (Budd–Chiari syndrome)
5. Any venous thrombosis anywhere in young adult
with low platelet and/or the neutrophil counts.
6. Idiopathic pancytopenia (IAA).

Laboratory findings and
diagnosis

Diagnosis of PNH
• Haemoglobinuria
• Haemosidrinuria
• Ham‟s test is positive in PNH. It shows
red cell lysis in serum at low pH
• Flow cytometry to look for the loss of
expression of GPI-linked proteins such as
CD55 and CD59.

Haemolytic anaemias types and causes-1.pdf

More Related Content

Similar to Haemolytic anaemias types and causes-1.pdf

Recently uploaded

Haemolytic anaemias types and causes-1.pdf