experts to recommend effective preventive meas-
ures.
Potential complications of both the multiple
myeloma and its treatments present risks that
affect the course of the cancer as well as the prog-
nosis (outlook). M-proteins bind with numerous
cell types, causing deposits to accumulate. Such
deposits on NERVEcells tend to cause NEUROPATHY
(pain or insensitivity). Such deposits within
organs, such as the LIVERand the kidneys, may
adversely affect their functions. Kidney damage
may result in kidney failure and the need for dial-
ysis. As well, chemotherapy agents and high-dose
corticosteroids, standards of treatment for multiple
myeloma, present the potential for numerous
adverse effects. Most people who have multiple
myeloma experience several periods of remission
ranging from six months to two years in duration
with each course of treatment.
See also AMYLOIDOSIS; CANCER TREATMENT OPTIONS
AND DECISIONS; IMMUNOGLOBULIN; LEUKEMIA; LY M-
PHOMA.
myelocyte See BONE MARROW.
myelodysplasia syndrome Different constella-
tions of symptoms, all arising from dysfunction of
the BONE MARROW and all leading to various
cytopenias (low BLOODcell counts). In myelodys-
plasia, also called preleukemia, the number of
hematopoietic cells within the BONE marrow
increases but the produced cells are disordered
and often released to the BLOODwhile they are
immature. Myelodysplasia syndrome most com-
monly affects people over age 60. Doctors do not
know what causes this syndrome though a signifi-
cant percentage of people who develop myelodys-
plasia have had exposure to industrial chemicals
(notably benzenes) or radiation. Children who
develop myelodysplasia often have underlying
genetic disorders such as DOWN SYNDROME.
Myelodysplasia may affect any of the blood cells,
resulting in a sometimes confusing clinical picture
of mixed symptoms such as bleeding (PLATELET
involvement) in combination with ANEMIA(ERY-
THROCYTEinvolvement) or with frequent infections
(LEUKOCYTE involvement). The SPLEEN often
becomes enlarged (SPLENOMEGALY) as it attempts to
filter defective blood cells from the blood and acti-
vate its hematopoietic functions to increase blood
cell production in compensation for the bone mar-
row’s inability to meet the body’s needs. In some
people myelodysplasia syndrome progresses to
chronic or acute LEUKEMIA. Examination of the
blood cells in a blood sample and bone marrow
biopsy allow the doctor to make the diagnosis.
Treatment may include transfusions of the deficient
blood components and ANTIBIOTIC MEDICATIONS as
necessary to treat infections. The outlook depends
primarily on the type of blood cells involved.
See also BLOOD TRANSFUSION; ENVIRONMENTAL HAZ-
ARD EXPOSURE; HEMATOPOIESIS; INFECTION; LYMPHOMA.myelofibrosis A chronic, degenerative condition
of the BONE MARROW in which fibrous tissue
replaces the red BONEmarrow. Researchers do not
know what causes myelofibrosis, which typically
develops in people between the ages of 50 and 70,
but believe it is an autoimmune response from a
single defective blood STEM CELL(called a clonal
dysfunction). The IMMUNE SYSTEMfails to recognize
the deformed cells and produces antibodies to
attack them. Because all BLOODcells originate from
BLOOD STEM CELLS, the attacking antibodies cause
extensive damage within the bone marrow. The
body’s efforts to repair this damage result in per-
vasive SCAR formation that progressively shuts
down the bone marrow.
The most apparent consequence is severe ANE-
MIA, as 99 percent of the bone marrow’s produc-
tion is oxygen-bearing erythrocytes (red blood
cells). The shortfall activates the body’s reserve
erythropoietic functions in the LIVER and the
SPLEEN, which begin producing erythrocytes. How-
ever, these organs cannot meet the demand and
so both begin to enlarge with the effort
(HEPATOMEGALYand SPLENOMEGALY, respectively).
Symptoms of myelofibrosis include those of
anemia as well as bone PAIN, easy bleeding, and
low resistance to infection as a consequence of
diminished LEUKOCYTE(white blood cell) produc-
tion. Blood tests show a low ERYTHROCYTEcount,
often low leukocyte and PLATELET counts, and
characteristic “tear drop” deformity of the erythro-
cytes. Bone marrow biopsy shows the infiltration
of fibrous tissue.
Treatment targets boosting the blood’s erythro-
cytes by BLOOD TRANSFUSIONand ERYTHROPOIETIN(EPO)160 The Blood and Lymph