Myelophthisic
AnemiaThis is a normocytic, normochromic anemia where the bone marrow
is wasting away (“phthisis”) secondary to another process. The other process
can be a tumor that metastasizes into the bone marrow, a granulomatous process
(Tuberculosis, lupus etc.) or a lipid storage disease. Most commonly the displacement
stems from cancers that metastasize into bones, particularly breast cancer and
prostate cancer. Others that invade the bone less often are kidney, lung, thyroid
and adrenal cancer. The principle here is that the bone marrow, which is the source
of all of the precursors of the blood cells, gets displaced. A primary process
of “myelofibrosis” can also occur where fibrous tissue forms in the bone marrow
space. This can later get calcified and is called “myelosclerosis”. The body
can compensate for the loss of bone marrow through a process of “myeloid metaplasia”.
This refers to hematopoiesis (production of blood cells) in the liver, the spleen
and in lymph glands. A rare genetic cause is Albers-Schoenberg
disease, where there is osteopetrosis, a calcification of the bones, which
leads to fractures. Often splenic infarcts and a myelophthisic anemia with myeloid
metaplasia are associated with this condition. Symptoms
These are the same
as the general symptoms of lassitude, lack of energy and other symptoms described
in the introductory chapter to anemia. In addition there are symptoms from the
underlying condition. With massive splenomegaly there is abdominal pressure and
a feeling of fullness early during a meal. There may also be left upper abdominal
pain from abdominal wall muscle spasm. With hepatomegaly there are similar symptoms
in the right upper abdomen. Diagnostic tests If
a normocytic anemia is present in a patient with splenomegaly a myelophthisic
anemia is suspected. This is further determined by a blood smear that will show
a leuko-erythroblastic pattern (nucleated red blood cells and immature myeloid
cells). The morphology of the red blood cells shows high variation, different
shapes and sizes. The hematologist can diagnose the condition from these parameters.
There is also a low platelet count with giant, bizarre looking platelets. Reticulocytes
are also often increased (may be prematurely released from the bone marrow and
the extra-medullary sites.) The final confirmatory test is a bone biopsy, which
may be difficult to get, but shows a typical pattern. X-rays of bones may show
bony areas from myelosclerosis. There may also be osteoblastic or osteolytic lesions
from bone tumors or metastases. Treatment The underlying
condition has to be treated. In cases where the cause is not known (so-called
“idiopathic form”) supportive treatment is given. This consists of between
20,000 and 40,000 units of erythropoietin. (EPO), given subcutaneously, once or
twice per week. Corticosteroids are also often given (10mg to 30mg of prednisone
daily by mouth). Unfortunately not every patient responds to this. For an enlarged
spleen hydroxyurea is given once or every other day (500 mg by mouth). The RBC
and spleen normalizing effect of hydroxyurea is very slow; it takes ½ year to
1 year to see results. Thalidomide has an immune modulating effect and can be
given as well, but it has serious side-effects (rash, neurotoxicity and high blood
pressure).
|
|
