The myelodysplastic syndromes

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The myelodysplastic syndromes


The myelodysplastic syndromes (MDS) are a group of clonal disorders of the bone marrow. Their common feature is bone marrow failure as a result of ineffective haematopoiesis rather than reduced haematopoietic activity. A hypercellular marrow and peripheral blood cytopenia with characteristic dysplastic morphological abnormalities form the basis for diagnosis. In early disease there is increased apoptosis of marrow progenitors causing peripheral blood cytopenia but in later MDS there is actually decreased apoptosis with characteristic gene mutations, enhanced survival of myeloblasts and potential expansion of a leukaemic clone. Patients may develop frank acute myeloid leukaemia (AML; see p. 40). Increased marrow angiogenesis and autoimmunity also occur.


MDS is predominantly a disease of the elderly, although it may affect all ages. It can arise de novo or follow previous chemotherapy or radiotherapy for another malignancy. It seems to be increasing in incidence.



Classification


This is not straightforward. The French-American-British (FAB) classification divides MDS into five subtypes depending on morphological features and particularly the number of blood and marrow leukaemic blast cells. The more recent WHO system (Table 25.1) divides MDS into unilineage or multilineage dysplasia, refractory anaemia with ring sideroblasts and dysplasia with excess blasts. The FAB entity chronic myelomonocytic leukaemia (CMML) is now included in the overlap ‘MDS with myeloproliferative disorder’ category. It is likely that cytogenetic and molecular abnormalities will be increasingly incorporated into the classification; a current example is 5q− syndrome, a distinct subtype of MDS associated with a response to novel therapy and a good prognosis.



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Jun 12, 2016 | Posted by in HEMATOLOGY | Comments Off on The myelodysplastic syndromes
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