and on the presence of cells foreign to
the marrow. It is useful in the diagnosis
of many blood disorders, including leu-
kaemiaand anaemia. It can also show
whether bone marrow has been invaded
by lymphomaor cells from other tumours.
bone marrow transplantThe techni-
que of using normal red bone marrow
to replace cancerous or defective mar-
row in a patient. In allogeneic bone
marrow transplantation (BMT), healthy
bone marrow is taken from a donor who
has a very similar tissue-type to the
recipient’s (usually a brother or sister).
In autologous BMT, the patient’s own
healthy bone marrow is harvested while
his or her disease is in remission and is
reinfused later. BMT is used only in the
treatment of serious, mostly potentially
fatal, blood and immune system disor-
ders, including severe aplastic anaemia
(see anaemia,aplastic), sickle cell anae-
mia, and leukaemia. An alternative
treatment is stem-celltransplantation,
in which cells from the umbilical cord of
a newborn baby or bloodstream of an
adult are used instead of bone marrow.
Before transplantation, all of the reci-
pient’s marrow is destroyed by cytotoxic
drugsor radiation in order to prevent
rejection of the donated cells and to kill
any cancer cells present. The donor
bone marrow is transfused into the cir-
culation from where cells find their way
to the bone marrow cavities and start to
grow. In autologous BMT, the patient’s
bone marrow is stored by cryopreserva-
tion. Before being frozen, the marrow is
usually treated to eliminate any unde-
tected cancerous cells. If the patient’s
disease recurs, the stored marrow can
then be reinfused.
The major risks with BMT are infection
during the recovery period and rejection
(known as graft-versus-host disease, or
GVHD). Immunosuppressant drugsare
used to prevent and treat rejection. The
risk of GVHD may be reduced by remov-
ing the T-cellsfrom the bone marrow
using monoclonal antibodies (see anti-
body, monoclonal) before reinfusion.
GVHD does not occur with allogeneic
BMT or stem-cell transplantation.
bone tumourA bone swelling that may
be cancerous (see bone cancer) or non-cancerous. The most common type of
noncancerous bone tumour is an osteo-
chondroma. Other types are osteomaand
chondroma (see chondromatosis). Treat-
ment is only necessary if the tumour
becomes very large or causes symptoms
by pressing on other structures. In such
cases, the tumour can be removed by
surgery. Osteoclastoma (also called a
giant cell tumour), which usually occurs
in the arm or leg of a young adult, is ten-
der and painful and has to be removed.
boosterA follow-up dose of vaccine,
given to reinforce or prolong immunity
after an initial course of immunization.
borborygmisee bowel sounds.
borderline personality disorderA
personality disorder that falls between
neurotic and psychotic levels. Mood
changes are often rapid and inappro-
priate. Angry outbursts are common, as
are impulsive, self-damaging acts such
as gambling or suicide attempts.
Bornholm diseaseOne of the names
for epidemic pleurodynia, an infectious
viral disease that is characterized by
severe chest pains and fever.
bottle-feedingInfant feeding using a
milk preparation usually based on mod-
ified cow’s milk. Formula milk contains
similar proportions of protein, fat, lac-
tose (milk sugar), and minerals as those
in human milk, but it lacks the protective
antibodies that are present in breast
milk. Vitamins are added. Bottle-fed
babies are at higher risk of gastrointes-
tinal infections than breast-fed babies
and may be more likely to develop aller-
gic disorders. (See also feeding, infant.)
botulinum toxinA potentially lethal
toxin produced by the bacterium CLOS-
TRIDIUM BOTULINUM (see botulism). In
tiny doses, botulinum toxin is used as a
drug to control muscle spasms in some
disorders (see blepharospasm; facial
spasm). It is also sometimes injected
into facial muscles to reduce visible
wrinkles temporarily.
botulismA rare but serious form of poi-
soning caused by eating improperly
canned or preserved food contaminated
with a toxin produced by the bacterium
CLOSTRIDIUM BOTULINUM. The toxin causes
progressive muscular paralysis as well
as other disturbances of the central andBONE MARROW TRANSPLANT BOTULISMB