lymphocytic or lymphoblastic leukaemia.
If abnormal cells are derived from other
types of white cell or their precursors,
the disease is called myeloid,myelo-
blastic, or granulocytic leukaemia. (See
also leukaemia, acute;leukaemia, chronic
lymphocytic;leukaemia, chronic myeloid.)
leukaemia, acuteA type of leukaemia
in which excessive numbers of immature
white blood cells called blasts are pro-
duced in the bone marrow. If untreated,
acute leukaemia can be fatal within a
few weeks or months. The abnormal
cells may be of 2 types: lymphoblasts
(immature lymphocytes) in acute lym-
phoblastic leukaemia, and myeloblasts
(immature forms of other types of white
cell) in acute myeloblastic leukaemia.
Exposure to certain chemicals (such
as benzene and some anticancer drugs)
or high levels of radiation may be a cause
in some cases. Inherited factors may also
play a part; there is increased incidence
in people with certain genetic disorders
(such as Fanconi’s anaemia) and chro-
mosomal abnormalities (such as Down’s
syndrome). People with blood disorders
such as chronic myeloid leukaemia (see
leukaemia, chronic myeloid) and primary
polycythaemiaare at increased risk, as
their bone marrow is already abnormal.
The symptoms and signs of acute
leukaemia include bleeding gums, easy
bruising, headache, bone pain, enlarged
lymph nodes, and symptoms of anaemia,
such as tiredness, pallor, and breath-
lessness on exertion. There may also be
repeated chest or throat infections. The
diagnosis is based on a bone marrow
biopsy. Treatment includes transfusions
of blood and platelets, the use of anti-
cancer drugs, and possibly radiotherapy.
A bone marrow transplantmay also be
required. The outlook depends on the
type of leukaemia and the age of the
patient. Chemotherapyhas increased
success rates and 6 in 10 children with
the disease can now be cured, although
treatment is less likely to be completely
successful in adults.
leukaemia, chronic lymphocyticA
type of leukaemiacaused by prolifera-
tion of mature lymphocytes. Although it
is incurable, the disease is not always
fatal. The cause is unknown.Symptoms develop slowly, often over
many years. As well as symptoms and
signs common to acute forms of leuk-
aemia (see leukaemia, acute), there may
be enlargement of the liverand spleen,
persistent raised temperature, and night
sweats. Diagnosis is by blood tests and
a bone marrow biopsy. In many mild
cases, no treatment is needed. To treat
severe cases, anticancer drugsare given,
sometimes with radiotherapy.
leukaemia, chronic myeloidA type of
leukaemia, also called chronic granulo-
cytic leukaemia, which is caused by the
overproduction of granulocytes, neutro-
phils,or polymorphonuclear leukocytes
(see blood cells). The cause is unknown.
This type of leukaemia usually has 2
phases: a chronic phase, which may last
for several years, and a more cancerous
phase, which is known as the blastic,
accelerated, or acute phase.
During the chronic phase, symptoms
may include fever, night sweats, and
weight loss. Visual disturbances, abdom-
inal pain, and priapismmay also occur.
The symptoms of the more cancerous
phase are like those of the acute forms
of leukaemia (see leukaemia, acute). The
diagnosis is made from blood tests and
a bone marrow biopsy. Treatment of the
chronic phase includes anticancer drugs.
When the disease transforms into the
acute phase, treatment is similar to that
given for acute leukaemia.
leukocyteAny type of white blood cell.
leukodystrophiesA rare group of in-
herited childhood diseases in which the
myelinsheaths that form a protective
covering around many nerves are des-
troyed. These diseases cause severely
disabling conditions, such as impaired
speech, blindness, deafness, and para-
lysis, and are always fatal.
leukoplakiaRaised white patches on
the mucous membranesof the mouthor
vulva, caused by tissue thickening. It is
most common in the elderly and is
increasingly found in people with AIDS.
Leukoplakia in the mouth, which most
commonly occurs on the tongue, is
usually due to tobacco-smokingor to
rubbing by a rough tooth or denture. It
is not known what causes the condition
to develop on the vulva.LEUKAEMIA, ACUTE LEUKOPLAKIAL