I
ANAEMIA
it is a complication of some other dis-
ease, and in such cases it is called
secondary. Conditions that may lead to
amyloidosis include
multiple myeloma
(a
cancer of bone marrow),
rheumatoid
arthritis,
familial
Mediterranean
fever,
tuberculosis,
and
other
longstanding
infections such as chronic
osteomyelitis
(bone
infection).
Amyloid
is
also
deposited in the brain in
Alzheimer’s dis-
ease.
Small deposits of amyloid are a
normal feature of
aging.
SYMPTOMS AND SIGNS
The
symptoms
of amyloidosis vary,
depending on the organs affected and
the duration of the condition. Affected
organs typically become enlarged. An
accumulation of amyloid in the heart
may result in
arrhythmias
(disturbances
of the heart rate or rhythm) and
heart
failure
(reduced pumping efficiency of
the heart). If the stomach and intestines
are affected, symptoms such as diar-
rhoea may develop, and the lining of
these organs may become ulcerated.
Primary amyloidosis is often charac-
terized by deposits of amyloid in the
skin, which appear as slightly raised,
waxy spots. Deposits of amyloid in
the kidneys may cause
kidney failure,
which can be fatal.
TREATMENT
There is no treatment for the removal of
amyloid deposits. However, it is possible
to halt the progression of secondary
amyloidosis by treatment of the under-
lying disorder.
amyotrophic lateral sclerosis
See
motor neuron disease.
amyotrophy
Shrinkage or wasting away of a muscle,
caused by a reduction in the size of its
fibres, leading to weakness. Amyotrophy
is usually the result of poor nutrition,
reduced use of the muscle (as occurs
when a limb is immobilized for a long
period), or disruption of the blood or
nerve supply to the muscle
(as can
occur in
poliomyelitis
or
diabetes mel-
litus).
(See also
atrophy.)
anabolic steroids
See
steroids
,
anabolic
.
anabolism
The manufacture of complex molecules
such as
fats
and
proteins
from simpler
molecules by metabolic (chemical and
physical) processes in living cells. (See
also
catabolism; metabolism.)
anaemia
A condition in which the concentration
of the oxygen-carrying pigment
haemo-
globin
in the blood is below normal.
Haemoglobin
molecules
are
carried
inside red
blood cells
and transport
oxygen from the lungs to the tissues.
Normally, stable haemoglobin concen-
trations in the blood are maintained by
a balance between red-cell production
in the bone marrow and red-cell des-
truction in the spleen. Anaemia may
result if this balance is upset.
TYPES AND CAUSES
Anaemia is not a disease in itself but a
feature
of many
different
disorders.
There are various types, which can be
classified into those due to decreased or
defective red blood cell production by
bone marrow
(see
anaemia, aplastic
;
anaemia
,
megaloblastic;
anaemia
,
iron-
deficiency
) and those due to decreased
survival of the red cells in the blood
(see
anaemia, haemolytic).
The illustrated
box shows the main types of anaemia.
SYMPTOMS
The symptoms common to all forms of
anaemia result from the reduced oxy-
gen-carrying capacity of the blood, and
the severity of symptoms depends on
how low the haemoglobin concentra-
tion has become. Slightly reduced levels
can cause tiredness, and lethargy Sev-
erely reduced levels can cause breathing
TYPES AND CAUSES OF ANAEMIA
Anaemia results either from reduced or defective production or an excessively
high rate of destruction of oxygen-carrying red blood cells. Four of the main
types are shown below, but anaemia can have many other causes (such as
various forms of leukaemia).
Iron-deficiency anaemia
Lack of iron prevents the
bone marrow from making
sufficient haemoglobin for
the red cells. The cells
produced are small and pale
and have a reduced oxygen-
carrying capacity.
Haemolytic anaemia
This type includes all
anaemias in which the rate
of red-cell production is
normal or high but in
which the cells are
destroyed at a much faster
rate than normal.
Megaloblastic anaemia
A deficient supply of
certain vitamins causes
the bone marrow to produce
red cells that are larger
than normal; they also
have a reduced oxygen-
carrying capacity.
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