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A clinical condition known as leukopenia occasionally
occurs in which the bone marrow produces very few
white blood cells, leaving the body unprotected against
many bacteria and other agents that might invade the
Normally, the human body lives in symbiosis with
many bacteria, because all the mucous membranes of
the body are constantly exposed to large numbers of
bacteria. The mouth almost always contains various
spirochetal, pneumococcal, and streptococcal bacteria,
and these same bacteria are present to a lesser extent
in the entire respiratory tract. The distal gastrointestinal
tract is especially loaded with colon bacilli. Furthermore,
one can always find bacteria on the surfaces
of the eyes, urethra, and vagina. Any decrease in the
number of white blood cells immediately allows invasion
of adjacent tissues by bacteria that are already
Within 2 days after the bone marrow stops producing
white blood cells, ulcers may appear in the mouth
and colon, or the person might develop some form of
severe respiratory infection. Bacteria from the ulcers
rapidly invade surrounding tissues and the blood.
Without treatment, death often ensues in less than a
week after acute total leukopenia begins.
Irradiation of the body by x-rays or gamma rays, or
exposure to drugs and chemicals that contain benzene
or anthracene nuclei, is likely to cause aplasia of the
bone marrow. Indeed, some common drugs, such as
chloramphenicol (an antibiotic), thiouracil (used to
treat thyrotoxicosis), and even various barbiturate
hypnotics, on very rare occasions cause leukopenia,
thus setting off the entire infectious sequence of this
After moderate irradiation injury to the bone
marrow, some stem cells, myeloblasts, and hemocytoblasts
may remain undestroyed in the marrow and are
capable of regenerating the bone marrow, provided
sufficient time is available.A patient properly treated
with transfusions, plus antibiotics and other drugs to
ward off infection, usually develops enough new bone
marrow within weeks to months for blood cell concentrations
to return to normal.