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Myelodysplastic syndrome
The myelodysplastic syndromes are a collection of haematological
conditions including:
Refractory anaemia (RA)
Refractory anaemia with ring sideroblasts (RARS)
Refractory anaemia with excess of blasts (RAEB)
Chronic myelomonocytic leukaemia (CMML) - not to be confused with CML
All the conditions show abnormalities in the production of one or more
of the cellular components of blood (red cells, white cells (other than
lymphocytes) and platelets (or their progenitor cells, megakaryocytes).
These abnormalities include:
neutropenia, anaemia and thrombocytopenia (low cell counts of each)
abnormal granules in cells, abnormal nuclear shape and size
chromosomal abnormalities, including chromosomal translocations.
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Epidemiology
It is estimated that 7,000 to 12,000 new cases of myelodysplastic
syndrome are diagnosed each year in the U.S.
These are mostly conditions of the elderly. However, there is an
increased risk in those people who have had chemotherapy for other
tumors.
Signs and symptoms
Anaemia - chronic tiredness (in this condition blood transfusion is the
only effective treatment, which can carry on for years)
Neutropenia (low white cell count) - increased susceptibility to
infection
Thrombocytopenia (low platelet count) - increased susceptibility to
bleeding
Because the cellular function is impaired the effects of low cell counts
may be greater than in other conditions with a similar cell count be
less impairment of normal function.
All these conditions have an increased risk of developing acute
leukaemia, which is notoriously resistant to treatment ("secondary
leukaemia"). In RA and RARS the risk is relatively low and the condtion
may persist for many years (eg 10). In RAEB and CMML the time course is
typically quicker.
Clinical suspicion
Normocytic anemia & reticulocytopenia not
diagnosed conventionally will require a bone marrow aspirate and subsequently
a bone marrow biopsy OR macrocytic anemia not found to be due to folate
or B12 deficiencies. More advanced cases may present with evidence of myelodysplasia.
Diagnosis
Required investigations include:
Refractory anemia (RA)
CBC: Macrocytic anemia with reticulocytopenia.
Bone marrow: The myeloid and megakaryocytic series in the bone
marrow appear normal, but megaloblastoid erythroid hyperplasia is present.
Dysplasia is usually minimal.
Refractory anemia with ringed sideroblasts (RAS)
The blood and marrow are identical to those in patients with
RA, except that >15% of marrow red cell precursors are ringed sideroblasts.
Refractory anemia with excess blasts (RAEB)
Clinical suspicion: There is significant evidence of disordered
myelopoiesis and megakaryocytopoiesis in addition to abnormal erythropoiesis.
Diagnosis: The marrow contains 5% to 20% myeloid blasts, and
1% to 5% of blasts may circulate in the blood.
Refractory anemia with excess blasts in transformation (RAEB-t)
Clinical suspicion: This is a panmyelosis
Diagnosis: 20% to 30% of marrow cells are blasts and >5% blasts
are seen in the blood. Auer rods may be seen.
Chronic myelomonocytic leukemia (CMML)
Clinical suspicion: Hepatosplenomegaly may be present.
Mild thrombocytopenia & mild anemia associated with morphologically
normal megakaryocytes & red cell precursors in the marrow may be present.
Diagnosis: The marrow contains 5% to 20% blasts, and the circulating
monocyte count is >1000 per cubic millimeter.
Treatment
No treatment (watch and wait)
Conservative (eg periodic blood transfusion)
Chemotherapy (although often patients do not tolerate chemotherapy
well).
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