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Pathophysiology
Molecular
pathology and
clinical
presentation
Diagnosis
Management
The author
ASSOCIATE PROFESSOR
P JOY HO,
senior staff specialist in
haematology, Royal Prince
Alfred Hospital; and clinical
associate professor, University
of Sydney, NSW.
The thalassaemias
Background
IN multicultural Australia with a
population of diverse ethnic origins,
the transfusion-dependent haemoblobinopathies are a significant
problem. This article aims to provide an overview of the thalassaemias, one of the main haemoglobinopathies we encounter, with
emphasis on the diagnosis and management of this genetically inherited
condition.
Ethnic origins of thalassaemia
Alpha thalassaemia occurs throughout south-east Asia, the Pacific
Islands, the Mediterranean, West
Africa, the Middle East and in parts
of the Indian subcontinent. Beta
thalassaemia is most common in the
Mediterranean, the Middle East,
North and West Africa, the Indian
subcontinent and south-east Asia,
including China, Thailand, the
Malay peninsula and Indonesia.
Information about ethnic origins of
patients in a multicultural country
such as Australia is therefore very
helpful. It is, however, important to
note that ethnic/inheritance history
can often lack accuracy and specificity, especially in a country where
intermarriage is common, and that
thalassaemia can occur sporadically,
so a patient’s ethnic origin cannot
be used to rule out thalassaemia.
In the ‘evolution’ of how thalassaemia was distributed among different ethnic groups, malaria is considered to be an important factor,
as carriers of thalassaemia may have
been more resilient to malaria infection and therefore survived preferentially by a process of natural
selection.
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18 March 2011 | Australian Doctor |
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HOW TO TREAT The thalassaemias
Pathophysiology
Pathophysiological
mechanisms
THALASSAEMIA is a
genetic disease associated
with the reduced production
of one of the globin chains
that consititute the haemoglobin (Hb) molecule.
Haemoglobin, the oxygencarrying moiety of the
human red blood cell, comprises two alpha-like and
two beta-like globin subunits. Both alpha and beta
thalassaemias are autosomal
recessive disorders (see Molecular pathology, below).
Alpha thalassaemia results
from a deficiency of alpha
globin chains. This leads to a
relative excess of beta globin
chains, which precipitate in
erythroid precursors and red
blood cells in the peripheral
blood. In the marrow the
excess of beta globin chains
leads to ineffective erythropoiesis, while in peripheral
blood, haemolysis of abnormal red cells is also an
important component of the
pathophysiology.
In contrast, beta thalassaemia is characterised by
reduced production of beta
globin chains, leading to a
relative excess of alpha
chains. The pathophysiology
of beta thalassaemia mainly
occurs in the marrow, as the
excess alpha chains precipitate in the erythroid precursors, leading to intramedullary destruction and
ineffective erythropoiesis.
Figure 1: α and ß globin gene clusters, with the globin chains and haemoglobins produced during each stage of development. The α
and ß globin clusters are found on chromosomes 16 and 11, respectively, with the globin genes arranged in the order of their
expression (and unexpressed pseudogenes designated ψ). These produce the ζ , α , ε , γ , δ and ß globin chains, which form the
tetramers of the embryonic, fetal and adult haemoglobins.
Figure 2: Developmental changes in human globin production. In the first 6-8 weeks of gestation, erythrocytes contain the embryonic
haemoglobins, which are then replaced by fetal hemoglobin (HbF, α2γ2 ). A second major switch to HbA (α2 ß2) occurs in the perinatal
period.
Regulation of globin
production
The genes encoding the
alpha and beta globin chains
occur in clusters; the alpha
globin gene cluster is on
chromosome 16, and the
beta globin gene cluster is on
chromosome 11. The globin
genes are arranged in the
order of their expression
during development (figure
1).
There are two adult alpha
globin genes, α1 and α2. In
contrast, the beta globin
gene is the only major betalike globin gene expressed
in the normal adult (expression of the delta [δ] and
gamma [γ] genes is minimal). Thus each normal
individual has four alpha
globin genes and two beta
globin genes. Over the years
it has become clearer how
the two globin gene clusters
are regulated, with the
genes
chronologically
arranged and expressed,
involving their promoters
and interactions with control elements and transcription factors.
As shown in figure 2, in
the first 6-8 weeks of gestation, erythrocytes contain
embryonic Hbs, which are
then replaced by fetal
haemoglobin (HbF α2γ2 ). A
second major switch to
HbA (α 2β 2), from gamma
to beta chain production,
occurs in the perinatal
period, such that haemoglobin in the adult comprises
predominantly HbA (about
97%), with small amounts
of HbA2 (α2δ2, 2.5-3.5%)
and HbF (0.5%). Thus,
while the alpha-like globin
chain production undergoes
a single switch, from embryonic (ζ ) to fetal/adult (α) in
embryonic life, beta-like
globin chain production
undergoes two switches,
from embryonic (ε) to fetal
(γ), and then from fetal to
adult (β,δ).
Molecular pathology and clinical presentation of alpha and beta thalassaemia
Alpha thalassaemia
ALPHA thalassaemia can result
from the deletion of one to all four
alpha globin genes. This results in
the reduced production of alpha
globin chains, such that the excess
beta globin chains aggregate to
form multimers, designated Hb
Barts (four gamma chains) or HbH
(four beta chains). More rarely,
mutations (nucleotide changes in
the DNA coding sequence) can also
cause alpha thalassaemia.
The clinical severity of alpha thalassaemia therefore depends on the
number of genes deleted. The loss
of all four genes leads to the condition of Hb Barts hydrops fetalis,
and is usually not compatible with
life. The loss of three genes is the
only symptomatic form of alpha
thalassaemia, known as HbH disease. The loss of 1-2 genes leads to
asymptomatic carriership of alpha
thalassaemia, that is, the individual is clinically well, but the abnormal alpha gene configurations may
be inherited by their progeny.
In Hb Barts hydrops fetalis the
affected fetus has gross pallor,
oedema, and massive hepato-
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splenomegaly. This condition is
usually incompatible with life and
the fetus is stillborn between 28
and 40 weeks’ gestation.
In HbH disease the affected
person has a mild anaemia with an
Hb of 70-100g/L and does not usually have major clinical problems.
These individuals are generally not
transfusion-dependent but, during
times of physical stress such as
infection, they are susceptible to
increased haemolysis and may need
to be transfused.
Individuals with deletion of one
or two alpha genes are asymptomatic carriers. Those who have
two genes deleted from the same
chromosome (--/αα) can be
denoted heterozygous α 0, while
those individuals with one alpha
gene deleted from each chromosome (α-/α-) can be denoted
homozygous α+.
The importance of making this
distinction lies in predicting possible genotypes of progeny (that is,
the risk of HbH disease or Hb
Barts hydrops fetalis if the partner
is also a carrier). Patients with a
single alpha gene deletion are also
completely asymptomatic.
It is important to distinguish carriers of alpha thalassaemia from
patients with iron deficiency, as the
FBC parameters and blood film can
show similar features, with
hypochromic microcytosis, pencil
cells, teardrop poikilocytes and
target cells (see Laboratory investigations, page 30). Making this distinction will avoid treating thalassaemia carriers inappropriately
with iron.
Beta thalassaemia
While alpha thalassaemia is mostly
caused by deletions of alpha globin
genes, beta thalassaemia is predominantly caused by single nucleotide
mutations of the beta globin gene.
More than 200 such mutations
have been characterised and are
classified as β+ or β0, depending on
whether the particular mutation
reduces or abolishes the production of beta globin chains, respectively.
Beta thalassaemia is an autosomal recessive disease. A normal
individual inherits one copy of the
beta globin gene from each parent.
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Thus, inheriting one copy of a
mutated beta globin gene results in
an asymptomatic beta thalassaemia
carrier (also called thalassaemia
trait or thalassaemia minor),
whereas inheriting two copies of
mutated beta globin genes, one
from each parent, results in the
severe clinical syndrome of thalassaemia major, described below.
HbE, which also affects the beta
globin gene, is the most common
cause of a beta thalassaemia syndrome in parts of south-east Asia
such as Thailand. It results from a
specific protein change in the beta
globin gene (position 26, Glu to
Lys), leading to abnormal processing and mild instability of beta
globin. Compound heterozygotes
for HbE and beta thalassaemia (ie,
a HbE mutation of one beta globin
gene, and a beta thalassaemia
mutation of the other gene)
develop a beta thalassaemia major
syndrome, whereas homozygotes
for HbE (ie, a HbE mutation of
both beta globin genes) and heterozygotes for HbE (ie, a HbE
mutation of one beta globin gene
and the other beta globin gene is
normal) have microcytosis but are
asymptomatic. It is important to
identify these HbE homozygotes
and heterozygote carriers for HbE
because of the possibility of a thalassaemia major syndrome developing in a child who co-inherits a
HbE and a beta thalassaemia mutation.
The terms thalassaemia major,
minor and intermedia refer to the
severity of the clinical syndromes
that occur. The clinical presentations of these are described below.
Beta thalassaemia major
The clinical presentations of beta
thalassaemia major are due either
to the condition itself, complications of its treatment (principally
iron overload), or both.
Anaemia and its complications.
Patients with thalassaemia major
have a severe clinical syndrome.
They usually present within the
first year of life with failure to
thrive, malaise or infection, and,
due to the anaemia, are transfusion-dependent for life.
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HOW TO TREAT The thalassaemias
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increased by coexistent conditions
such as hepatitis C.
Iron-overload cardiomyopathy is
the most important cause of mortality in thalassaemia major
patients. If not reversed, cardiomyopathy can result in progressive
debilitation and death. Fatal ventricular arrhythmias can occur suddenly.
The function of many endocrine
glands is affected by iron overload.
Growth failure can occur in up to
30% of patients. Factors contributing to this include:
• Problems with general health (eg,
anaemia, cirrhosis, cardiomyopathy).
• Specific endocrine factors (such
as disturbances of the growth
hormone axis, delayed puberty
and hypothyroidism).
• Deficiencies of folate and zinc.
Hypogonadotrophic hypogonadism can result in impaired
sexual development and infertility
in up to 50% of thalassaemia
major patients due to pituitary
iron deposition.
Diabetes occurs in 3-10%, usually after age 10. It is relatively
common in poorly chelated
patients (ie, patients who do not
achieve adequate iron load reduction with chelation therapy).
In untransfused beta thalassaemia major patients, as occurs in
countries where transfusion provisions are lacking, severe problems
may develop due to the untreated
anaemia, and due to the ‘compensatory’ expansion of marrow at the
sites of red cell production, which
would normally involute after
birth, such as the liver, spleen and
bone.
Iron overload. Iron overload is a
major cause of morbidity and mortality in transfusion-dependent thalassaemia major patients. In addition to the iron that is derived from
the breakdown of transfused red
cells, there is also an increase in
iron absorption from the gut,
resulting from the deregulation of
controls of iron metabolism, such
as reduced hepcidin, a molecule
that normally inhibits iron absorption in iron-replete individuals. The
body has no mechanism for excreting excess body iron.
Iron overload affects multiple
organs, including the liver, heart
and endocrine glands. Iron accumulation in the liver can lead to
liver fibrosis and cirrhosis and can
be complicated by hepatocellular
carcinoma. The risk of cancer is
Major causes of thalassaemia intermedia
• Inheritance of mild beta thalassaemia mutations in compound heterozygosity
or homozygosity
• Co-inheritance of alpha thalassaemia in homozygotes or compound
heterozygotes of beta thalassaemia mutations
• Heterozygotes of beta thalassaemia who have inherited additional alpha
globin genes
• The inheritance of hereditary persistence of fetal Hb in patients with two beta
thalassaemia genes (HbF compensates for the lack of HbA)
• Compound heterozygotes of beta thalassaemia and other beta chain
variants, eg, HbE
• Compound heterozygotes of β and δβ thalassaemia*
*The severity of δβ thalassaemia (deletion of δ and β globin genes) is modulated by the
upregulation of γ globin production
Hypothyroidism occurs in 310%, but is relatively uncommon
in well-chelated patients.
Hypoparathyroidism has an
estimated incidence of about 7%.
Osteoporosis is an increasing
cause of morbidity, given the
improved life expectancy. Possible
factors include hypogonadism,
hypothyroidism, chronic hepatitis,
the deleterious effect of desferrioxamine (one of the available iron
chelators) on bone and collagen
synthesis, as well as poor nutrition and exercise.
Other transfusion risks. These
include viral infections and transfusion reactions. Some older
patients who were transfused
before the screening of blood
products were infected with hepatitis C, which can exacerbate the
liver complications of iron overload.
Beta thalassaemia trait
(minor/carriers)
Patients with a single copy of a β0
or β+ thalassaemia gene are completely asymptomatic. The Hb level
is usually normal or only mildly
abnormal (ie, >100g/L). Clearly it
is important to diagnose beta thalassaemia carrier status in the prenatal or antenatal setting, and to
distinguish it from iron deficiency.
Beta thalassaemia intermedia
Beta thalassaemia intermedia is a
relatively rare condition compared
with beta thalasaemia trait and
beta thalasaemia major. It is clinically defined as a thalassaemia syndrome that is not as severe as
transfusion-dependent thalassaemia major, yet not asymptomatic like beta thalassaemia trait.
There is a wide spectrum of severity; from a mild anaemia of 8090g/L with elevated ferritin and
mild splenomegaly, to a more
severe anaemia of Hb 70-80g/L
with more severe splenomegaly
and more frequent transfusion
requirement. The genotypic causes
of thalassaemia intermedia are
varied and are listed in the box,
left. In each category the most
important principle is the degree
of imbalance between alpha and
beta-like globin chains.
Although these patients do not
need regular transfusions, they can
still develop significant iron overload due to increased iron absorption and the cumulative iron load
of intermittent transfusions.
Diagnosis of alpha and beta thalassaemia
THE diagnosis of alpha and
beta thalassaemia is based
on clinical features and laboratory investigations.
Figure 3: Blood films of thalassaemia syndromes. A: Normal. B: Alpha thalassaemia trait. C: Beta
thalassaemia trait. D: HbH disease. E: Haemoglobin Barts hydrops fetalis. F: Beta thalassaemia
major.
Clinical features
Clinical features of HbH disease (symptomatic alpha
thalassaemia), beta thalassaemia major and beta thalassaemia intermedia have
been described in the section
above. The characteristic
severe presentation of beta
thalassaemia major in the
first year of life is unmistakeable, with anaemia and failure to thrive. A child with
undetected HbH disease
could present when an
episode of increased haemolysis is precipitated by
stresses such as infection.
• FBC, which includes Hb,
MCV, MCH, red cell count
A
B
• Examination of blood film
• Iron studies
• Hb electrophoresis
performed in alkaline and
acid conditions
• Hb high-performance liquid
chromatography (HPLC)
C
• HbH bodies
D
• Genetic diagnosis when
indicated
Laboratory investigations
These are summarised in the
box, right, and the details
described below.
Alpha thalassaemia
Single alpha gene deletion is
usually ‘silent’ clinically and
on routine blood tests, such
that hypochromic microcytosis is often not present (or
there may be a very slight
reduction in mean corpuscular volume [MCV] and mean
corpuscular haemoglobin
[MCH]), with a normal Hb
level and blood film, and
genetic diagnosis is required
to define this anomaly. HbH
bodies are often not demonstrated, in contrast to a
double alpha gene deletion.
In antenatal or prenatal
diagnosis, if one parent is a
carrier with αα/--, it is
important to know whether
the other parent has a single
alpha gene deletion to deter-
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| Australian Doctor | 18 March 2011
Investigations for the
diagnosis of
thalassaemia
E
F
mine the likelihood of HbH
disease in the child.
In contrast, with a double
alpha gene deletion, the
blood film shows the characteristic features of a thalassaemia carrier, with
hypochromic microcytosis
and occasional teardrops
and elliptocytes (figure 3B).
MCV and MCH are
reduced. The HbA2 level is
normal, unlike in beta thalassaemia trait, when there
is an increase in HbA2. HbH
bodies, demonstrated by a
special stain on blood films,
are usually seen.
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However as the detection
of HbH bodies can be difficult, DNA analysis is the
only definitive test for alpha
thalassaemia and may be
required to establish whether
alpha thalassaemia carrier
status is present or not.
In HbH disease (deletion
of three alpha globin genes),
Hb is 70-100g/L, with low
MCV and MCH, and typical thalassaemia changes on
the blood film (figure 3D).
These changes are more
severe than in double alpha
gene deletion but not as
marked as in beta thalassaemia major (figure 3F).
HbH bodies (consisting of
precipitated Hb bound to
the cell membrane) are
clearly seen by special
supravital staining.
In contrast, the blood
film of a fetus with Hb
Barts hydrops fetalis is
markedly abnormal, with
many nucleated red cells,
hypochromia, basophilic
stippling, elliptocytes and
teardrop poikilocytes (figure
3E).
Beta thalassaemia
The FBC and blood film of a
beta thalassaemia carrier
(figure 3C) is indistinguishable from that of a double
gene deletion alpha thalassaemia carrier (figure 3B),
with hypochromic microcytosis being the most prominent feature. The level of Hb
can be normal or slightly
reduced. The diagnostic feature is a raised HbA2. However, this can be masked by
coexistent iron deficiency. It is
therefore necessary to repeat
an HbA2 measurement after
a patient is iron replete to
obtain an accurate result. In
the antenatal setting, genetic
diagnosis may have to be performed due to time constraints (see Antenatal screening, page 32).
In contrast the laboratory
findings in a patient with beta
thalassaemia major are significantly different, with
severe anaemia and gross thalassaemic changes (see figure
3F) — marked aniso-poikilocytosis, hypochromic microcytosis, basophilic stippling,
target cells, elliptocytes, and
teardrop poikilocytes.
Hb electrophoretogram (Hb
EPG) and high-performance
liquid chromatography
In Hb electrophoresis,
haemoglobin molecules,
normal and abnormal, are
separated in a gel via an
electric current. The main
species of Hb that are
demonstrated are HbA,
HbA2, HbF, and the abnormal beta globin tetramers
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HOW TO TREAT The thalassaemias
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a gradient of increasing ionic
strength. It is a highly efficient
method of analysing and quantifying Hbs, and complements Hb EPG.
that occur in alpha thalassaemia,
such as Hb Barts and HbH, as well
as the Hb variants (due to non-thalassaemic globin gene mutations)
such as HbE, HbC and HbS (of
sickle cell disease). Characteristic
Hb EPGs performed under alkaline
conditions are shown in figure 4.
Acid electrophoresis is performed
to confirm and separate unresolved
Hb bands.
In a normal adult the predominant Hb is HbA (α2β2), accounting
for 95-97.5%, with a small amount
of HbA2 (α2δ2) of ~2.5-3.5%.
Table 1 summarises the different
findings of thalassaemia carrier
status, HbH disease, beta thalassaemia major and sickle cell disease.
High-performance liquid chromatography (HPLC) is a more
recent development by which Hb
molecules are separated using ion
exchange as blood is eluted through
Genetic diagnosis of thalassaemia
In difficult cases, especially in prenatal settings (see below), genetic
or molecular diagnosis of thalassaemia may be required.
As most alpha thalassaemia is
caused by deletions, the main
method of diagnosis is using PCRbased methods. In contrast, as
most beta thalassaemia is caused
by single base mutations, while a
number of PCR-based methods are
used, sequencing techniques may
be required if common mutations
are not found by PCR.
Certain mutations tend to be
more common in some geographical areas. Thus in some laboratories, PCR-based methods are first
applied to focus on the most
Figure 4: Hb electrophoresis under alkaline conditions. A and
B: Normal HbA and HbA2. C: Heterozygous HbS. D: Normal.
E: Heterozygous HbE. F: Infant with increased HbF. G: HbSC.
A
B
C
D
E
In our institution, the standard
tests specified for antenatal screening of any pregnant woman comprises FBC, HPLC and iron studies.
In our area in central Sydney the
decision was made to perform
HPLC as an initial screen to avoid
missing carriers of HbS who have
normal MCV and MCH, but programs from other areas may differ.
Iron studies are important for
two main reasons:
• The finding of hypochromic
microcytosis may be the result of
iron deficiency, which is common
in pregnancy and must be corrected.
• The presence of iron deficiency
can be the cause of a false-negative beta thalassaemia screen, that
is, if a patient is iron deficient,
this may mask a raised HbA2.
Hence the diagnosis of beta-thalassaemia is not excluded, as the
HbA2 may be ‘erroneously’ low.
common mutations, and sequencing may be performed subsequently
if required or for excluding coinheritance of both alpha and beta
forms of thalassaemia.
F
G
— HbA
— HbF
— HbS
— HbE,
HbC,
HbA2
position
Antenatal screening
Antenatal screening programs for
thalassaemia and other haemoglobinopathies such as sickle cell disease
are crucial in any antenatal clinic,
and full diagnostic services must be
offered. In many areas antenatal clinics are conducted with a ‘shared-care’
program in conjunction with GPs of
the area. The investigations required
often need to be based on the ethnic
mix of a catchment population. For
example, in an ethnically diverse
area, especially where there can be a
lot of intermarriage between ethnic
groups, the risk of thalassaemia or
haemoglobinopathy cannot be reliably ascertained by the history of a
patient’s ethnic origin.
When this occurs in a non-pregnant
patient, iron supplementation may
first be administered to render the
patient iron-replete, then the HbA2
is repeated. When it is more urgent
to determine the thalassaemia carriership status of a parent in the antenatal setting, genetic studies should
be performed as soon as possible.
Screening of family members is
often helpful in identifying those
who are thalassaemia carriers, and
therefore determining the risk of
thalassaemia carriage in the pregnant woman.
Each clinical genetics unit in public
hospitals should have an antenatal
screening program for the haemoglobinopathies. As a detailed discussion
of antenatal screening is not the aim
of this article, the family practitioner
should consult the clinical genetics
or obstetrics units with which they
are associated for details of the
policy.
Table 1: Results of Hb electrophoresis in common haemoglobinopathies
Condition
HbA (%)
HbA2 (%)
HbF (%)
HbS (%)
Normal
95-98
<3.5
<1
0
Beta thalassaemia minor
90-95
>3.5
1-3
0
Beta thalassaemia major (β0β0)
0
1-4
>95
0
Beta thalassaemia intermedia
<20
1-4
>75
0
Alpha thalassaemia carrier
(one deletion: αα/α-)
95-98
<3.5
<1
0
Hb Barts <3% at birth;
trace HbH
Alpha thalassaemia carrier
(two deletions: αα/- - or α-/α-)
95-98
<3.5
<1
0
Hb Barts 3-8% at birth;
HbH <2%
HbH disease (three deletions: α-/- -)
70-95
1-2
<1
0
Hb Barts <5%; HbH 5-30%
Hb hydrops fetalis (four deletions: - -/- -)
0
0
0
0
Hb Barts 70-80%; HbH <5%;
Hb Portland† 10-15%
Sickle cell trait
50-60
<3.5
<2
35-45
Sickle – β+ thal
5-30
>3.5
2-10
65-90
Sickle – β0 thal
0
>3.5
2-15
80-90
Homozygous sickle cell disease*
0
<3.5
2-15
85-95
Hb Barts / HbH
*Sickle cell disease is a haemoglobinopathy caused by substitution of a valine residue for a glutamine residue in the beta globin chain, leading to sickle
haemoglobin (HbS). This leads to the propensity of Hb in red blood cells to polymerise in conditions of deoxygenated stress, forming fibrils within the red
cells, which assume a sickle shape and causes vaso-occlusion as well as haemolysis.
†
The embryonic Hb (ζ2γ2 — see figure 1).
Management of thalassaemia
Beta thalassaemia major
Transfusion
IN Australian haematology
units, adult patients with
beta thalassaemia major are
generally transfused every
four weeks, with 2-4 units
packed red cells per episode
for adults. In children the
volume of transfusion is calculated by weight. The frequency and amount of transfusion are guided by a
transfusion target of a pretransfusion Hb of 90-100g/L
haemoglobin. Patients are
transfused with phenotyped
blood to reduce the chances
of developing allo-antibodies. In the past, white blood
cell filters were used to prevent transfusion reactions.
However, with leucodepletion of packed red cells, this
is no longer necessary.
In the past, thalassaemia
major patients commonly
underwent splenectomy to
reduce red cell sequestration
34
and haemolysis and therefore to reduce transfusion
requirements. This is now
less ‘routinely’ performed,
with one suggested approach
being to consider splenectomy when transfusion
requirements increase by
50% or more over one year.
Splenectomised patients
require vaccinations for
pneumococcus, meningococcus and haemophilus
influenzae.
Iron chelation therapy
As noted earlier, one of the
most important aspects of
management is iron chelation to prevent and/or treat
the significant clinical complications of iron overload,
described earlier in this article.
The mainstay of iron
chelation for many years
was desferrioxamine. Due to
a short half-life and poor
oral bioavailability, desfer-
| Australian Doctor | 18 March 2011
rioxamine had to be administered by subcutaneous infusion using a pump, for 5-7
nights a week. Not surprisingly, this regimen had a
negative impact on compliance (adherence). Lack of
compliance with iron chelation therapy is one of the
most common causes of
mortality, usually due to iron
overload cardiomyopathy.
More recently, two oral
iron chelators have become
available — deferiprone and
deferasirox. Their oral route
of administration has
improved compliance, but
problems can still occur.
Deferiprone is taken three
times a day, and deferasirox
is administered daily. They
have different side-effect
profiles, and the choice of
agent can be made according to individual tolerance.
The characteristics of the
three iron chelators are summarised in table 2. Multiple
studies have demonstrated
the effectiveness of both oral
agents. Other studies have
shown the benefit of using
oral deferiprone and subcutaneous desferrixoamine in
combination, particularly in
the reduction of cardiac iron.
Studies of other combinations such as deferasirox and
desferrioxamine are also
being planned.
In patients who have
developed cardiomyopathy,
constant 24-hour chelation
is considered to be necessary
to remove cardiac iron and
reverse cardiomyopathy.
This is usually administered
in the form of IV desferrioxamine through an in-situ IV
device.
At each transfusion visit,
patients are monitored for
FBC, electrolytes, LFTs and
iron studies.
Serum ferritin is the most
accessible and commonly
used means of monitoring
www.australiandoctor.com.au
iron load, although it is not
always an accurate reflection
of total body iron. Multiple
studies have shown serum
ferritin to correlate closely
with the incidence of cardiac
impairment and survival.
However, ferritin can be
raised by many confounding
factors, such as the acutephase reactions of infection,
inflammation or malignancy,
or due to hepatic damage.
Thus serum ferritin values
should not be interpreted in
isolation; the trend or average of ferritin values over a
period such as three months
is much more informative.
Creatinine is monitored
together with testing of urine
for protein, as one of the
iron chelators, deferasirox,
can sometimes result in
impaired renal function. In
patients using deferiprone,
weekly blood counts are
required due to the risk of
neutropenia and a small risk
of agranulocytosis. LFTs are
important for monitoring
iron overload, viral hepatitis and of the side effects of
chelation (especially oral
iron chelators).
Endocrine tests, including
pituitary function, thyroid
function tests, parathyroid
hormone, sex hormones and
cortisol, are performed at
least on an annual basis.
Random glucose testing is
usually done in the biochemical screen, and fasting glucose and glucose tolerance
tests can be performed when
indicated. Bone mineral density and vitamin D measurements are also performed as
required.
New methods of monitoring
iron overload
New methods of monitoring
iron load have been developed. Although liver biopsy
was previously considered
the gold standard for assess-
A D _ 0 3 5 _ _ _ MA R 1 8 _ 1 1 . p d f
ing liver iron, it was never
widely adopted in Australia
due to the invasiveness of
the procedure and the inaccuracies of sampling variation. It may still be performed for assessment of
fibrosis, cirrhosis and hepatocellular carcinoma.
More recently, MRI has
been successfully adapted to
measure iron load both in
the liver and the heart. In
Australia, the use of MRI for
this purpose has not yet been
reimbursed by the government and most patients have
gained access to the investigation through clinical studies. It is hoped that MRI for
this purpose may become
more accessible to patients
in the future.
The importance of
multidisciplinary care
Multidisciplinary care is very
important in the management
of beta thalassaemia major
patients. This includes cardiology, gastroenterology, hepatology, endocrinology, gynaecology and fertility services,
ophthalmology and ENT/
audiometry, psychology/psychiatry as well as social work
input. Some of the pertinent
issues are presented in the
box, above right.
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Issues in multidisciplinary care
• A yearly echocardiogram or gated heart pool scan is usually performed to monitor cardiac
function; review by a cardiologist is arranged on a regular basis.
• LFTs must be reviewed at least every three months. Patients with underlying hepatitis C can be
treated with antiviral therapy to attempt eradication. Successful viral clearance is more likely if iron
load is kept well controlled. Complications such as liver fibrosis and cirrhosis are managed as per
usual practice. As both increased iron load and viral hepatitis are risk factors for the development
of hepatocellular carcinoma, monitoring by yearly measurement of alpha-fetoprotein is performed.
Patients may require regular review by hepatologists.
• Regular endocrinology review is also required. Endocrine complications such as growth
impairment, hypogonadism, diabetes and hypothyroidism are managed as per established
practice.
• Gynaecology and fertility services are required especially in patients who are hypogonadal and
need assisted fertility to conceive. The management of pregnant patients with thalassaemia major
is covered in the text.
• Due to the side effects of some of the iron chelators (see table 2) patients require regular
monitoring by ophthalmologists and audiometry.
• Compliance with iron chelation therapy is an important determinant of prognosis. In addition, the
complications of thalassaemia major and its treatment can have significant effects on
psychological wellbeing. Clinical psychologists/psychiatrists should be closely involved when
problems are encountered.
Table 2: Summary of available iron chelators, characteristics of
administration, excretion and side effects
Characteristic
Desferrioxamine
Deferiprone
Deferasirox
Therapies in development
and research areas
Usual dose
20-60mg/kg/day
75-100mg/kg/day
20-40mg/kg/day
Route
SC/IV
Usually SC over 8-12
hours 5-7 nights a week
PO
Three times
a day
PO
Once a day
Half-life
20-30 min
3-4 hours
8-16 hours
Alpha thalassaemia
(HbH disease)
Excretion
Urinary, faecal
Urinary
Faecal
HbH disease is the only
symptomatic form of alpha
thalassaemia. While there is
a spectrum of severity, in
general the clinical presentation of these patients is
much less severe than for
patients with beta thalassaemia major.
They are not transfusiondependent, and need treatment mainly at times of
increased peripheral haemolysis as a result of concurrent illness, such as infections. Patients may benefit
from folate supplementation
to support increased erythropoiesis. During acute presentations and haemolytic
crises, patients may require
transfusions and treatment
with antibiotics.
Less frequently, more
severely affected patients
may have a significantly low
Main side
effects
• Injection site lumps,
infections
• Bone changes
• Ototoxicity
• Ophthalmic changes
• Arthralgia/
arthritis
• Abnormal LFTs
• Neutropenia,
agranulocytosis
• Rash
• Diarrhoea, nausea
• Abnormal renal function
(reversible, non-progressive)
• Abnormal LFTs
baseline haemoglobin that
impairs their quality of life,
and splenectomy can be considered to reduce transfusion
requirements. It is also rare
for iron chelation to be necessary but patients with a
heavier transfusion history
may develop iron overload.
Gallstones are detected in
more than 30% of asymptomatic patients.
Management of the
pregnant patient with
beta thalassaemia major
The most important cause
of morbidity and mortality
in a pregnant beta thalassaemia major patient is car-
chelator once they become
pregnant, and to resume
desferrioxamine in the
second half of pregnancy.
Transfusion requirements
usually increase as pregnancy progresses; the Hb
should be kept above
100g/L.
There are few data on the
use of desferrioxamine in
lactation. The molecular
weight is small enough for
some excretion into breast
milk, but the effects, if any,
of exposure in a nursing
infant are unknown. In
many practices, unless the
mother has severe iron overload and is at risk of cardiomyopathy, breastfeeding
is encouraged for six weeks
after delivery without iron
chelation, followed by the
resumption of an appropriate chelation regimen after
breastfeeding is stopped.
There are no data on the use
of deferasirox or deferiprone
in lactation and therefore
neither is recommended.
diac decompensation in the
setting of iron-overload cardiomyopathy. As a result, it
is extremely important that
women with beta thalassaemia major do not
embark on pregnancy unless
their iron control is optimal.
Of the three iron chelators
in clinical use, only desferrioxamine can be used in
pregnancy, and should only
be used in the second half
of pregnancy, as there are
concerns regarding its effect
on fetal development when
used in early pregnancy. Our
usual advice to a woman
with beta thalassaemia
major is to stop their iron
In beta thalassaemia major
and intermedia, efforts have
been made to devise therapies to increase the production of HbF (α2γ2), to compensate for the deficiency in
beta chains and therefore
HbA. Such therapies include
hydroxyurea and DNAdemethylating agents, but
none have so far shown sufficient activity to emerge as
standard therapy in beta
thalassaemia.
Stem cell transplants from
HLA-identical siblings have
been
performed
and
achieved cure, mainly in
children, but the morbidity
and mortality of the procedure is such that it is not
commonly done in Australia, especially when management by conventional
means — transfusion, iron
chelation and multidisciplinary care — has resulted in a
marked improvement in the
prognosis and quality of life
of these patients.
Gene therapy remains a
long-held goal in the cure of
beta thalassaemia major,
and research is ongoing.
Conclusion
THE management of thalassaemia is a highly specialised discipline. In Australia the thalassaemias and
haemoglobinopathies are
commonly encountered and
the GP will undoubtedly see
cases in their daily practice.
It is hoped that this article
provides a good overview
of diagnosis and management of this condition.
While much of the management is undertaken in specialist haematology units, it
is very important for the
GP to be able to recognise
medical presentations and
to undertake treatment or
refer for specialist care as
appropriate.
Summary
• The thalassaemias are a
significant problem in the
Australian population, with
its diverse ethnic make-up.
• Alpha and beta
thalassaemias are inherited,
autosomal recessive
diseases associated with
the reduced production of
alpha and beta globin
chains, respectively.
• Clinical presentations for
the thalassaemias range
from asymptomatic carriers
to severely affected,
transfusion-dependent beta
thalassaemia major.
• The diagnosis of the
thalassaemias requires an
understanding of laboratory
tests and correlation with
clinical syndromes.
• An understanding of the
genetic abnormalities,
inheritance patterns and
the genotype–phenotype
relationship is crucial in
antenatal diagnosis.
• The management of beta
thalassaemia major is
multidisciplinary and
includes regular
transfusions as well as the
management of iron
overload; in contrast HbH
disease (the symptomatic
form of alpha thalassaemia)
is generally less severe.
Online resources
• Thalassaemia Australia:
www.thalassaemia.org.au
• Thalassaemia NSW:
www.thalnsw.org.au
Author’s case study
LOUISE, 35, has beta thalassaemia
major. She started regular transfusions when she was less than one
year old, and started desferrioxamine
infusions for iron chelation at age
five. She attends the haematology
unit of a major hospital every four
weeks, receiving transfusions of three
units of packed red cells each time.
She works as a hairdresser.
When she was in her teens she was
trained to perform the subcutaneous
injections of desferrioxamine herself
five nights a week (the drug is
infused through a pump over 8-10
hours on each of those nights) but
she was often non-compliant with
this therapy. Due to this non-compliance, her ferritin often rose to the
2000-2500μg/L level. (The target ferritin level for people using chelation
is 1000μg/L.) She had regular psychological counselling to address the
issue of non-compliance.
In her early 20s Louise’s attitude
changed significantly and she became
much more compliant and her ferritin levels fell to 1000-1500μg/L.
About four years ago the decision
was made to change the desferrioxamine to one of the oral iron chelators, deferasirox. She first obtained
this through a clinical trial, and later
through hospital pharmacy prescription. Through the clinical study she
gained access to liver and cardiac
MRI, which showed that liver and
cardiac iron were within the ideal
range. She takes the oral iron chelator once a day, and although she initially had diarrhoea, this settled
promptly.
Her serum creatinine and LFTs are
monitored monthly. Her ferritin
levels are satisfactory at 1200μg/L.
Apart from the iron chelator, she is
also receiving hormonal replacement,
as she was found to be hypogonadal,
and calcium and vitamin D, as bone
mineral density has shown osteopenia. She has had no cardiovascular
symptoms, but undergoes yearly
echocardiography, and is seen by the
cardiologists as required, usually
every 12 months.
She was diagnosed with hepatitis C
in the late 1980s and has been folwww.australiandoctor.com.au
lowed up by hepatologists, undergoing
interferon treatment for the hepatitis,
but unfortunately this was unsuccessful in clearing the virus. Combination
therapy for hepatitis C (interferon plus
ribavirin) is currently contraindicated
in thalassaemic patients, as the main
toxicity of ribavirin is haemolysis. It is
hoped that she may undergo further
treatment if newer antiviral agents for
hepatitis C become available.
She was married at 30; her partner
was tested and did not have thalassaemia. She initially had trouble conceiving a child. As a result she underwent ovulation induction and gave
birth to a healthy baby boy two years
ago.
cont’d next page
Acknowledgements
I would like to acknowledge
Professor Ron Trent for his
review of the sections on
genetic diagnosis, and
thanks to Sydney Yuen,
Konstantinos Zarkos and
Thavorn Jurinkulranavish
for assistance with the
figures.
Conflict of interest
Dr Ho has been an advisory
board member of Novartis
(deferasirox) and received
conference support and
honoraria for lectures, and
conference support from
Orphan (deferiprone).
18 March 2011 | Australian Doctor |
35
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HOW TO TREAT The thalassaemias
GP’s contribution
DR DAVID SENA
Dee Why, NSW
Case study
MR RP, 38, is an immigrant of
Spanish–Italian descent, married to a 34-year-old Armenian
woman. He had never had a
medical and came in for a
checkup, as he planned to start
a family.
His father died of pneumonia in his early 40s, and he
was aware of a history of
anaemia and liver problems in
paternal uncles living overseas.
His wife was well, and
unaware of any related family
conditions.
Symptomatically RP felt
well, smoked four cigarettes
and drank 40g alcohol daily.
He had never had a transfusion and took no medications
or vitamin supplements.
He was a tanned overweight
man of Mediterranean appear-
ance, with a BMI of
31.7kg/m2. Physical examination was normal apart from
mild hypertension (152/92
mmHg) and a just-palpable
liver (1-2cm).
Routine laboratory testing
was carried out, with the following results:
• FBE: Hb 126g/L (normal
range 130-180); MCV 62fL
(80-100); MCH 19pg (2634); RCC 6.5 × 1012/L (4.05.9 × 1012/L).
• Platelet and WCC counts:
normal, no retics. Blood
film: red cells microcytic and
hypochromic.
• Iron studies: normal serum
iron and transferrin; total
iron-binding
capacity
43μmol/L (46-70); saturation 48% (10-45); ferritin
915μg/L (30-300).
• Biochemistry: normal renal
function and electrolytes.
LFTs: bilirubin 47μmol/L (020); GGT 64 U/L (0-45);
LDH 258 U/L (100-225).
• Haemochromatosis gene
typing: compound heterozygote (one copy of the C282Y
and H63D genes).
• Haemoglobin electrophoresis: HbA ~91%; HbA2
~7%; HbF ~3%.
Thus Mr RP appears to
have a hypochromic microcytosis with some evidence of
iron overload, relating to a
combination of beta thalassaemia minor and haemochromatosis.
Questions for the author
The priority here seems to be
to address the iron-overload
status caused by RP’s
haemochromatosis. Should I
offer venesection to reduce his
iron load or is there an alternative approach?
Beta thalassaemia trait may
aggravate the clinical picture
of HFE C282Y homozygotes
and increase the risk of iron
overload in patients with HFE
genotypes at a milder risk of
haemochromatosis (as in this
patient — compound heterozygotes of HFE C282Y and
H63D mutations account for
only 2-5% of phenotypic
haemochromatosis, with a
penetrance of <1.5%). However, it is still important to first
confirm that the elevated ferritin is the effect of iron overload and not an acute-phase
reactant, for example, infec-
How to Treat Quiz
2. Which TWO statements are correct?
a) Normal adults have four copies of the gene
that codes for alpha globin
b) In normal adults there is only one beta-type
globin chain produced by erythroid cells
c) In normal adults there are two copies of the
gene that codes for beta globin
d) In normal adults all haemoglobin consists of
two alpha chains with two beta chains (HbA,
α2β2)
3. Which TWO statements are correct?
a) In alpha thalassaemia there can be deletion of
from one to all four alpha globin genes
b) People who have lost two alpha genes have
symptomatic alpha thalassaemia (HbH
disease)
c) Loss of one or two alpha genes results in
asymptomatic alpha thalassaemia carriers
What is the significance of
RP’s abnormal LFTs?
These show a mildly raised
GGT and LDH, while the
bilirubin is more significantly
elevated (assuming normal
transaminases). The “just palpable liver” may be of concern, as it may indicate
hepatomegaly.
It is important not to immediately assume that the anomalies in RF’s LFTs are due to
iron accumulation
It would be helpful to test
whether the bilirubin is predominantly conjugated or
unconjugated. Relevant considerations include many possible scenarios — for example,
the elevated bilirubin which is
much ‘more abnormal’ than
the other LFTs may be due to
Gilbert’s syndrome if shown
to be unconjugated, the mildy
elevated GGT could be due to
his alcohol intake, while this
overweight patient may also
be susceptible to a fatty liver
that could be exacerbated by
the alcohol. A liver ultrasound
should be done, especially as
the liver is enlarged (which
does not usually occur in liver
iron overload).
What investigations should his
wife have with pre-pregnancy
genetic counselling?
She should have an FBC
and blood film, iron studies
and thalassaemia screen,
which comprises HbEPG with
measurements of HbA2 and
HbF, and examination for
HbH bodies.
General question for the
author
Hypochromic microcytic
anaemia with blood film findings suggestive of thalassaemia
trait is not uncommon in
ethnic communities from the
Mediterranean, south-east
Asia and northern Africa. Is it
relevant to establish a policy
for thalassaemia screening for
the busy time-poor GP?
As stated, in many areas in
Australia, antenatal clinics are
conducted with a ‘shared-care’
program in conjunction with
GPs. The same principles can
be applied for detecting carriers of thalassaemia and
haemoglobinopathies in general, as the concerns of thalassaemia carrier detection are
centred on, but not confined
to, the antenatal setting.
Thus, in central Sydney
close collaboration between
the clinical genetics, haematology and obstetrics departments established a protocol
of investigations for GPs in the
antenatal shared care program
to follow. This includes clear
guidance on what steps to take
according to particular test
results, including instances
when consultation with the
clinical genetics department is
required.
Importantly, investigations
should be based on the ethnic
mix of the population. Each
hospital or antenatal unit
should make a protocol for the
screening of the thalassaemias
and haemoglobinopathies, relevant to the area, available
and accessible to GPs, with
avenues for consultation with
the clinical genetics/haematology units.
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The thalassaemias
— 18 March 2011
1. Which TWO statements are correct?
a) In alpha thalassaemia there is a relative
excess of beta globin chains
b) In beta thalassaemia there is reduced
production of alpha-globin chains
c) The precipitation of excess globin chains in
alpha and beta thalassaemia results in red cell
destruction and ineffective erythropoiesis
d) In adults, two different alpha-like globin
chains are produced by erythroid cells,
resulting in HbA and HbA2
tion, inflammation or neoplasm. Once other causes of
an elevated ferritin have been
excluded, it would be reasonable to start venesection,
aiming to reduce the ferritin
to low-normal range.
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d) Symptomatic alpha thalassaemia (HbH
disease) is a more severe condition than beta
thalassaemia major
4. Which TWO statements are correct?
a) Loss of two alpha globin genes from the
same chromosome in a parent increases the
risk of HbH disease or hydrops fetalis in the
progeny
b) Beta thalassaemia is predominantly caused
by deletions of the beta globin genes
c) Inheriting two copies of a mutated beta globin
gene results in the severe clinical syndrome of
thalassaemia major
d) A child who co-inherits one HbE mutated
gene and one beta thalassaemia mutated
gene will be an asymptomatic carrier
5. Which TWO statements are correct?
a) The terms thalassaemia major, minor and
intermedia refer to the severity of the clinical
syndromes that occur
b) Patients with thalassaemia major usually
present with symptoms of anaemia in late
childhood
c) Patients with thalassaemia major are not
usually transfusion-dependent
d) In untransfused beta thalassaemia major
patients, there is ‘compensatory’ increase in
red cell production at sites such as the liver,
spleen and bone
6. Which TWO statements are correct?
a) The normal mechanisms for excreting iron are
ineffective in thalassaemia major
b) Iron accumulation in the liver can lead to liver
fibrosis, cirrhosis and hepatocellular
carcinoma
c) Iron-overload cardiomyopathy is not usually
clinically significant in thalassaemia major
d) Growth failure can occur in up to 30% of
patients with transfused thalassaemia major
7. Which TWO statements are correct
regarding thalassaemia major patients?
a) Impaired sexual development and infertility
are due principally to the effects of anaemia
b) Adequate iron-load reduction with chelation
therapy may prevent the development of
diabetes
c) Hypothyroidism is common despite adequate
iron-load reduction with chelation therapy
d) Osteoporosis is an important long-term
sequela of thalassaemia major and its
treatment
8. Which TWO statements are correct?
a) In thalassaemia carriers the Hb level is usually
normal or only mildly abnormal (ie, >100g/L)
b) Because thalassaemia intermedia patients do
not need regular transfusions, they do not
develop significant iron overload
c) In patients with two alpha gene deletions,
the HbA2 level is elevated
d) Elevated HbA2 in beta thalassaemia carriers
can be masked by coexistent iron deficiency
9. Which TWO statements are correct?
a) The characteristic gene deletions of alpha
thalassaemia are usually diagnosed by PCR
b) DNA sequencing may be required to
diagnose beta thalassaemia
c) Antenatal screening for alpha and beta
thalassaemia should be restricted to patients
of ethnicities known to be at high risk
d) In a pregnant woman who is iron deficient,
iron status should be normalised before
antenatal screening for thalassaemia
10. Which TWO statements are correct
regarding the management of
thalassaemia major?
a) The frequency and amount of transfusion are
guided by a post-transfusion target Hb of 90100g/L
b) Thalassaemia major patients routinely
undergo splenectomy to reduce red cell
sequestration and haemolysis
c) Splenectomised patients require vaccinations
for pneumococcus, meningococcus and
Haemophilus influenzae
d) Serial or average serum ferritin levels over
three-month periods are a useful measure of
body iron load
CPD QUIZ UPDATE
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complete this online along with the quiz at www.australiandoctor.com.au. Because this is a requirement, we are no longer able to accept the quiz by post or
fax. However, we have included the quiz questions here for those who like to prepare the answers before completing the quiz online.
HOW TO TREAT Editor: Dr Giovanna Zingarelli
Co-ordinator: Julian McAllan
Quiz: Dr Giovanna Zingarelli
NEXT WEEK Mitochondrial medicine represents a newly established, complex and evolving field. The first case of mitochondrial disease was described in 1962, but a multitude of clinical syndromes
and disorders have since been added to this subcategory of diseases. At least one in 250 Australians are at risk of developing mitochondrial disease during their lifetime. Find out more in next week’s
How to Treat. The authors are Dr Christina Liang, senior neuromuscular fellow, department of neurology, Royal North Shore Hospital, St Leonards; and Professor Carolyn Sue, professor and
director of neurogenetics, department of neurology and Kolling Institute of Medical Research, Royal North Shore Hospital, St Leonards, NSW.
36
| Australian Doctor | 18 March 2011
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