ANAEMIA, APLASTIC
A
difficulty on exercise, dizziness as a
result of reduced oxygen reaching the
brain,
angina pectoris
(chest pain due to
impaired oxygen
supply to the heart
muscle), and palpitations as the heart
works harder to compensate. General
symptoms include pallor, particularly of
the skin
creases,
the lining
of the
mouth, and the inside of the eyelids.
Other features may occur with partic-
ular forms of anaemia. For example,
some degree of
jaundice
occurs in most
types of haemolytic anaemia because
the high rate of destruction of red
blood cells leads to an increased level of
the yellow pigment bilirubin (produced
by the breakdown of the haemoglobin
in red cells) in the blood.
DIAGNOSIS
Anaemia is diagnosed from the patient’s
symptoms and by blood tests (see
blood
count).
A
bone marrow biopsy
(removal of
a small sample of bone marrow for
analysis) may be required to determine
whether or not red blood cell produc-
tion is defective.
anaemia, aplastic
A rare but serious type of
anaemia
(a
reduced level of the oxygen-carrying
pigment
haemoglobin
in the blood). In
aplastic anaemia, the red cells, white
cells, and platelets in the blood are all
reduced in number. The condition is
caused by a failure of the
bone marrow
to
produce stem cells, the initial form of
all blood cells.
CAUSES
Treatment of cancer with
radiotherapy
or
anticancer drugs
can temporarily inter-
fere with the cell-producing ability of
bone marrow, as can certain viral infec-
tions
and
other
drugs.
Long-term
exposure to insecticides
or benzene
fumes may cause more persistent aplas-
tic anaemia; and another recognized
cause is a moderate to high dose of
nuclear radiation. An
autoimmune disorder
(in which the immune system attacks
the body’ own tissues) is responsible in
some cases. Aplastic anaemia sometimes
develops for no known reason.
SYMPTOMS
A low level of red blood cells may cause
symptoms, such as fatigue and breath-
lessness, that are common to all types of
anaemia.
Deficiency
of white
cells
increases
susceptibility
to
infection,
resulting in frequent or severe infec-
tions; platelet deficiency may lead to a
tendency
to
bruise
easily,
bleeding
gums, and nosebleeds.
DIAGNOSIS AND TREATMENT
Aplastic anaemia is usually suspected
from the results of a blood test, particu-
larly a
blood count,
and is confirmed by
a
bone marrow biopsy
(the removal of a
small
sample
of bone
marrow
for
microscopic analysis).
Blood and platelet transfusions can
control symptoms. Immunosuppression
(therapy to suppress the immune sys-
tem) is used to treat aplastic anaemia
due to an autoimmune process. Severe
persistent aplastic anaemia may be fatal
without a
bone marrow transplant
.
anaemia, deficiency
Forms of
anaemia
(a reduced level of
the oxygen-carrying pigment
haemoglo-
bin
in the blood) caused by lack of one
or more substance that are essential for
normal
haemoglobin
synthesis
and
maintenance. Deficiency anaemia may
arise by various means, such as by
mal-
absorption
or insufficient dietary intake
of a particular nutrient.
Iron-deficiency
anaemia
and
megaloblastic anaemia
are
examples of deficiency anaemias.
anaemia, haemolytic
A form of
anaemia
(a reduced level of
the oxygen-carrying pigment
haemoglo-
bin
in the blood) caused by premature
destruction of red blood cells in the
bloodstream (see
haemolysis).
The bone
marrow has the capacity to increase its
red cell production approximately six-
fold
over
normal
rates.
Haemolytic
anaemia will result only if the shorten-
ing of the lifespan of red blood cells is
sufficiently
severe
to
overcome
the
reserve capacity of the bone marrow.
TYPES AND CAUSES
Haemolytic anaemias can be classified
in two ways: if the cause of the haem-
olysis is an abnormality of the red cells
themselves,
the
condition is
usually
inherited; if the cause of the haemolysis
is outside the cells, the condition is usu-
ally acquired later in life.
When haemolysis is due to a defect
within the red cells, the underlying
problem may be abnormal rigidity of
the cell membrane (the thin layer of tis-
sue surrounding each cell). This causes
the cells to become trapped, at an early
stage of their life-span, in the small
blood vessels of the spleen, where they
are destroyed by macrophages
(cells
that ingest foreign particles). Abnormal
rigidity may result from an inherited
defect of the cell membrane
(as in
hereditary
spherocytosis),
a defect of the
haemoglobin
in the cell (as in
sickle-cell
anaemia),
or a defect of one of the cell’s
enzymes.
An inherited deficiency of the
glucose-6-phosphate dehydrogenase en-
zyme (see
G6PD deficiency)
may result in
episodes of haemolytic anaemia since
the red cells are prone to damage by
infectious illness or certain drugs or
foods. One variety of G6PD deficiency
is
most
common
in
Mediterranean
countries (see
favism).
Haemolytic anaemias due to defects
outside the red cells fall into three main
groups. First are disorders in which red
cells are destroyed by buffeting (by arti-
ficial surfaces such as replacement heart
valves, abnormal blood-vessel linings,
or a blood clot in a vessel, for example).
In the second group, the red cells are
destroyed by the
immune system
. Im-
mune haemolytic anaemias may occur
if foreign blood cells enter the blood-
stream, as occurs in an incompatible
blood transfusion, or they may be due
to an
autoimmune disorder
(in which the
immune system attacks the body’s own
tissues). In
haemolytic disease of the new-
born,
the baby’s red cells are destroyed
by antibodies, produced by the mother,
crossing the placenta. Thirdly, the red
cells may be destroyed by microorgan-
isms in the blood; the most common
cause is
malaria
.
SYMPTOMS
People with haemolytic anaemia may
have symptoms common to all types of
anaemia, such as fatigue and breathless-
ness, or symptoms that are specifically
due to haemolysis, such as
jaundice
(caused by an excessive concentration
in the blood of bile pigments formed
from the destruction of red blood cells).
DIAGNOSIS AND TREATMENT
Diagnosis is confirmed by microscopic
examination of the blood (see
blood
film).
Treatment depends on the cause.
Some inherited anaemias can be con-
trolled by removing the spleen (see
splenectomy).
Others,
such
as
G6PD
deficiency and favism, can be prevented
by avoiding the drugs or foods that pre-
cipitate haemolysis. Anaemias due to
immune processes can often be con-
trolled
by
immunosuppressant drugs
.
Transfusions of red cells are sometimes
needed for emergency treatment of life-
threatening anaemia.
anaemia, iron-deficiency
The most common form of
anaemia
(a
reduced level of the oxygen-carrying
pigment
haemoglobin
in the blood).
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