Myelodysplastic syndromes (MDS) are a group of
clonal haemotopoietic stem cell diseases characterized by
cytopenia(s), dysplasia in one or more of the major myeloid
cell lines, ineffective haemotopoiesis, and increased
risk of development of acute myeloid leukemia[
1]. The
patients' symptoms are generally related to cytopenia(s).
The peripheral blood studies reveal cytopenia(s) and bone
marrow smears show dysplasia. Increased number of
blasts can be seen in a subset of cases but the count should
be less than 20%. According to the WHO classification
system they are evaluated in seven categories; refractory
cytopenia with unilineage dysplasia, refractory anemia
with ring sideroblasts (RARS), refractory cytopenia with
multilineage dysplasia (RCMD), refractory anemia with
excess blasts (RAEB), myelodysplastic syndrome associated
with isolated del 5q, myelodysplastic syndrome,
unclassifiable types and childhood myelodysplastic syndrome.
The major manifestation of refractory cytopenias is ineffective hematopoiesis of a single lineage and refractory
anemia is the most common symptom[
2].
In refractory cytopenias with multilineage dysplasia,
there are one or more blood cytopenias and dysplastic
changes in 10% or more of the cells in two or more myeloid
lineages[1]. For patients who meet this definition
of RCMD and whose marrow also show more than 15%
ring sideroblasts, the diagnosis should be “RCMD with
ring sideroblasts”. The possibilities of RAEB must be excluded
by ensuring that there are less than 1% circulating
blasts, less than 5% marrow blasts, and no Auer rods. The
possibility of chronic myelomonocytic leukemia must
also be excluded by establishing the absence of a monocytosis[3].
In RCMD, the frequency of cytogenetic aberrations,
incidence of acute leukemic progression, and overall
survival were noted to be intermediate between those patients
with RA or RARS and those with MDS with excess
blasts[3].
In summary, diagnosis of MDS should be considered
for patients with cytopenia in the peripheral blood whose
bone marrow samples show the presence of dysplasia in
one or more lineages. The subclassification also requires
the knowledge about the percentage of blasts in the blood
and bone marrow and whether or not ring sideroblasts
are present. Furthermore, the absolute monocyte count
should be less than 1x106/mm3 to exclude chronic myelomonocytic
leukemia which is in the differential diagnosis.
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