The myelodysplastic syndromes (MDS) are a heterogeneous group of haematological neoplasms characterized by ineffective and dysplastic haemopoiesis. The ineffectiveness of haemopoiesis is apparent from the usual coexistence of a hypercellular bone marrow and peripheral cytopenia. The responsible mutation occurs in a multipotent haemopoietic stem cell, although the defect in maturation may be apparent in only one or two lineages.
The incidence in adults is 3-4/100,000/year with the condition being about twice as common in men as in women. The incidence rises exponentially with age. Aetiological factors include anti-cancer chemotherapy and irradiation. There are also predisposing conditions, such as aplastic anaemia (congenital or acquired). MDS can evolve into acute myeloid leukaemia (AML), but in some patients death from the consequences of bone marrow failure occurs without transformation. A minority of patients who are transfusion-dependent die from iron overload.
In some patients the diagnosis is made incidentally, e.g. when a blood count done for another reason shows anaemia. Other patients present with features of bone marrow failure, such as infection, bleeding or symptoms of anaemia.
Haematological and pathological features
The blood film and bone marrow aspirate are critical in diagnosis. The peripheral blood may show cytopenia (anaemia, neutropenia, thrombocytopenia) and various dysplastic features (Figures 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9). Monocytes are sometimes increased and less often neutrophils or platelets. The dysplastic features that may be present include hypogranular neutrophils, hypolobated neutrophils and macrocytosis. A dimorphic blood film, sometimes with Pappenheimer bodies, is seen in sideroblastic anaemia; usually the two populations are: 1) hypochromic microcytes and 2) normochromic macrocytes. There may be platelets that are large, hypogranular or both. There may be circulating erythroblasts, myeloblasts, granulocyte precursors, monoblasts or promonocytes and immature monocytes.
Peripheral blood film of a patient with refractory anaemia (FAB and WHO classifications) showing anisocytosis. MGG, high power.
Peripheral blood film of a patient with refractory anaemia (FAB and WHO classifications) showing an oval macrocyte. The neutrophil is cytologically normal. MGG, high power.
Peripheral blood film of a patient with refractory anaemia with ring sideroblasts (FAB and WHO classifications) showing dimorphic red cells. MGG, high power.
Peripheral blood film of a patient with refractory anaemia with ring sideroblasts (FAB and WHO classifications) (same patient as Figure 10.3) showing dimorphic red cells and an erythrocyte with prominent Pappenheimer bodies. MGG, high power.
Peripheral blood film of a ...