Thalassaemia
Introduction
Thalassaemia is
an inherited blood disorder.
The incidence of
thalassaemia carriers varies greatly from country to country
throughout the world. It's very common in the Middle East, the
Indian sub-continent and through out South East Asia, in a region
including Southern China, Thailand, Malaysia and parts of the
southern Mediterranean. These regions coincide with areas where
malaria occurs. Thalassaemia trait is believed to offer some
resistance to malaria. Thalassaemia is common in those parts of the
world where malaria is endemic.
Blood is made up
of plasma (fluid), red blood cells, white blood cells and platelets.
The white cells protect your body against and fight infection and
the platelets are responsible for normal blood clotting. The red
blood cells carry red blood protein called haemoglobin. Haemoglobin
contains iron and transports oxygen from your lungs around the body.
Anaemia is caused by reduced haemoglobin. If the anaemia is mild it
does no harm and may not be noticeable.
A normal
haemoglobin molecule contains four protein (globin) chains (two
alpha globin chains and two beta globin chains) Different genes are
responsible for producing each chain. In thalassaemia there is an
inherited defect in one of these genes. If the alpha chain is
affected this causes alpha thalassaemia. If the beta chain is
affected this causes beta thalassaemia.
There are a
number of different types of thalassaemia within these groups, alpha
thalassemia being less diverse than beta thalassaemia.
Symptoms
Alpha
plus Thalassaemia
This is very common in some ethnic groups. There are no symptoms and
it usually goes unnoticed. There may be slight iron deficiency (anaemia)
if the blood is tested for some reason. Sometimes people may be
mistakenly diagnosed as having iron deficiency anaemia and be
treated with iron medications unnecessarily.
Alpha
Zero Thalassaemia
There are no symptoms and you are perfectly healthy. However if both
parents have alpha zero thalassaemia they have a 1 in 4 chance of
having a baby who has alpha zero thalassaemia major which is
incompatible with life; the baby is often born prematurely and is
dead or dies shortly after birth.
Beta
Thalassaemia Trait (Carrier)
There are usually no symptoms and you are perfectly healthy, however
there are an increased number of cells and they are smaller than
those without the condition. It can cause mild anaemia because
slightly less haemoglobin is produced than normal. This usually does
not usually cause you any symptoms and cannot be treated by
increased iron intake.
Beta
Thalassaemia major
Between birth and three to six months, your baby with Beta
thalassaemia major will seem normal and quite healthy. Your baby
will then begin to show symptoms of anaemia (they become pale) there
may be shortness of breath, jaundice and an enlarged spleen.
Without
treatment your child’s bones will grow abnormally and death will
occur early in childhood. Also if the condition is poorly treated or
between transfusions your child will be pale, lethargic and
breathless. There may be yellowing (jaundice) of the eyes and skin
due to excessive breakdown of red blood cells. Also with poor
treatment growth may be delayed, there may be osteoporosis of the
bones and the spleen may be damaged.
Causes
Thalassaemia is
an inherited disorder of the haemoglobin, (the substance in the
blood that carries oxygen to the tissues). It is caused by an
abnormal gene inherited from one or both your parents.
The haemoglobin
chains , i.e. alpha or beta globin chain are affected. There is a
decrease in the production of alpha globin chains in alpha
thalassaemia due to a deletion (missing) or mutation (abnormal
change) of one or more of the four alpha globin genes located on
chromosome 16.
Beta
thalassaemia is more varied due to the diversity of the mutations
(abnormal changes) in the beta globin gene. Beta thalassemias are
caused by mutations on chromosome 11.
Diagnosis
Many people who
carry thalassaemia do not know that they carry it. It is diagnosed
by having a simple blood test, to measure the size of red blood
cells and the amount of a type of haemoglobin in the blood.
Antenatal
screening is offered on the NHS, this allows you to undergo a blood
test to detect carrier couples and provide genetic counselling. You
should also be offered a choice of prenatal diagnosis, to allow an
informed choice concerning continuation or termination of any
affected pregnancy. Specialist counselling should also be available.
Chorionic villus sampling (CVS) is done at 10 weeks of pregnancy.
Fetal blood sampling is done between 18-20 weeks, and the more
rarely done amniocentesis test between 14-18 weeks.
Testing of
babies, at one year old is recommended in some areas in the UK to
give a clear diagnosis of carrier status.
If a member of
your family tests positive as a carrier for thalassaemia or you
suspect you may be a carrier then it is sensible that you get tested
and have genetic counselling if planning a baby. It is also
important that you are tested to avoid the mistaken diagnosis of
iron deficiency.
Treatment
Treatment for
Beta thalassaemia major involves you having regular blood
transfusions, which take place every six to eight weeks, depending
on the severity of the anaemia. Excess iron builds up in your body
from these regular transfusions. This is called iron overload. If
this is left untreated, iron will build up in your body, leading to
a condition called haemosiderosis. This can cause serious long-term
damage such as heart failure and liver failure.
Iron overload is
kept under control by treatment with a medicine called
desferrioxamine, to achieve a more normal level of iron in the body.
Desferrioxamine works by binding (the chemical term is “chelating”)
with the iron in your blood and the chelated iron is then removed by
the kidneys (excretion) from the body. Desferrioxamine has to be
given by injection, usually by a slow injection under the skin via a
small device or pump over eight to twelve hours. You may be taught
how to do this yourself at home. The amount of desferrioxamine and
how often it is given depends on the how much iron you have in your
body i.e. the amount of iron overload.
As you will be
receiving this medicine regularly (often daily), it can become
tiresome for you or your carer. So, it is important to understand
why desferrioxamine doses should not be missed. Sticking to
desferrioxamine treatment routines helps protect against serious
complications in later life, such as diabetes and heart disease.
There are also more immediate benefits such as prevention of nausea
and sickness caused by iron overload.
Deferipone is
another medicine used to treat iron overload. It works in a similar
way to desferrioxamine but is given by mouth. This medicine is only
given to patients in whom desferrioxamine is not suitable or is not
tolerated.
Like all
medicines, both desferrioxamine and deferipone may have side
effects. You should refer to the manufacturer’s patient information
leaflet for further information as well as talk to your doctor or
pharmacist if you have any particular concerns. If you are receiving
either of these medicines you need to be closely monitored by having
regular blood tests and eye and ear examinations. Checks on body
weight and height every three months may be carried out in children
because their growth can be affected by the condition and, in some
cases, by the medicines.
Beta
thalassaemia intermedia treatment may be the same as for Beta major
but as the anaemia is less severe, the need for transfusions or the
frequency of tranfusions and need for iron overload treatment will
be different according to the severity of the anaemia.
Supplementary treatment
The time taken
for iron to be removed from your body by desferrioxamine is improved
by taking a daily dose of ascorbic acid (vitamin C). This is
prescribed by your doctor according to your age and is usually
started one month after starting desferrioxamine treatment. Ascorbic
acid prescribed for this purpose should be taken separately from
food because it also increases the absorption of iron in food, which
you must avoid.
If you have
heart problems, you will not be given ascorbic acid because its
combined effect with the iron in the blood may make the heart
problem worse. Any other multivitamin and mineral supplements should
not be taken unless prescribed by a doctor because they can increase
or decrease absorption of iron and other minerals.
Other
Treatments
Venesection
- therapeutic removal of blood from the body - to help deal with
excess iron build -up
Surgery
– removal of the spleen (splenectomy)
is sometimes required if the spleen is damaged because it has to
remove a larger number of abnormal red cells from the circulation.
Management and reduction of iron in the diet
- usually only a small amount of iron is absorbed from the diet,
however the absorption is increased when haemoglobin in the blood is
low, as in beta Thalassaemia major. This is especially true between
transfusions. Therefore iron in the diet should be low (red meat is
especially high in iron). You should be referred to a dietician for
advice on diet.
Bone
marrow transplantation
– this can provide a cure for Beta thalassaemia major. Bone marrow
is transplanted from a matched unaffected sibling or unrelated
donor. It is best done when the child is very young. However, the
procedure is painful and, although success rates are improving, they
are unpredictable.
There are many
emotional, psychological and social effects for the person with
thalassaemia and their family, particularly as self- management is
so important. Psychological support is important in managing
chelation therapy and other aspects of the condition. You may find
getting involved with local support groups and voluntary
organisations helpful.
Healthcentral 2005
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