Diseases related to white cells. Leukopenia
The term leukopenia refers to leukocyte counts that
are abnormally low (below 4,000 per cubic millimetre).
Like leukocytosis, which is usually due to an increase
of neutrophils (neutrophilia), leukopenia usually is
due to a reduction in the number of neutrophils (neutropenia).
Of itself, neutropenia causes no symptoms, but persons
with neutropenia of any cause may suffer from frequent
and severe bacterial infections. The term agranulocytosis
refers to an acute disorder characterized by severe
sore throat, fever, and marked prostration associated
with extreme reduction in the number of neutrophilic
granulocytes or even their complete disappearance from
the blood.
Neutropenia may be due to a hypersensitivity mechanism
in which a drug provokes the formation of antibodies.
If the drug happens to bind to the neutrophil, the antibody
accidentally destroys the neutrophil when it reacts
with the drug. A second important mechanism of neutropenia
is toxic damage to the bone marrow. Chemotherapeutic
agents used in the treatment of cancer and leukemia
often produce leukopenia (and neutropenia) by damaging
the bone marrow. Drugs that cause neutropenia include
pain relievers, antihistamines, tranquilizers, anticonvulsants,
antimicrobial agents, sulfonamide derivatives, antithyroid
drugs, and chemotherapeutic agents used for the treatment
of cancerand leukemia.
Neutropenia also is associated with certain types of
infections (e.g., typhoid, brucellosis, measles) and
with certain diseases involving the bone marrow (e.g.,
aplastic anemia) or the spleen. In addition, sufficiently
high doses of radiation will cause neutropenia, as will
certain antitumour agents. Treatment includes removal
of the cause of the neutropenia and the use of antibiotics
appropriate for the existing infection.
