Clinical variants of MDS

CMML: classified as MDS/MPD in the WHO classification; clinical outcome relates to BM blast % rather than PB monocyte count (fflp234).

5q- syndrome: clinically distinct form of MDS in WHO classification; characterised by more indolent clinical course, lower rate of evolution to AML, macrocytic anaemia, thrombocytosis and dysplastic megakaryocytes

Pure sideroblastic anaemia (PSA): defined as sideroblastic anaemia with dysplasia confined to erythropoietic cells (RARS in WHO classification); survival better (77% OS at 3yrs) than where dysplastic features are also present in myeloid or megakaryocyte lineages (RCMD-RS in WHO classification; 56% OS at 3yrs) and very low risk of AML, even in the long 228 term.

Secondary MDS: incidence increasing due to successful chemotherapy and increased pollution; multiple chromosomal abnormalities in almost all patients; poorer prognosis than de novo MDS.

Hypoplastic MDS: <15% of cases of MDS have hypocellular BM on biopsy (<30% cellularity age <60; <20% aged >60); dysplastic megakaryocytes ± myeloid cells or excess blasts should be present; may be difficult to distinguish from aplastic anaemia in which pancytopenia usually more severe: cytogenetic findings typical of MDS may be necessary; no particular age range, FAB type and no difference in prognosis; may respond to immunosuppressive therapy.

Fibrotic MDS: up to 50% of cases have increased BM fibrosis but <15% have marked fibrosis; all FAB types; more common in secondary MDS; BM hypercellular with myelofibrosis; PB shows pancytopenia and dysplastic features and sometimes leucoerythroblastic picture; organomegaly unusual; rapid deterioration usual.

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