The myelodysplastic syndromes.

The concept of preleukaemia originated early in this century with the recognition of prodromal haematological abnormalities in acute myeloid leukaemia.' Since then similar preleukaemic disorders have 'been described, including primary acquired sideroblastic anaemia and smouldering or oligoblastic leukaemia. Confusion created by differing connotations placed on the term preleukaemia was resolved in 1982 by the introduction of a common nomenclature based on morphological criteria. Under the generic term of myelodysplastic syndromes five subgroups were defined: refractory anaemia; refractory anaemia with ring sidero-blasts; refractory anaemia with an excess of blasts; refractory anaemia with an excess' of blasts in transformation; and chronic myelomonocytic leukaemia.2 Other conditions associated with a risk of developing acute myeloid-leukaemia such as aplastic anaemia,. paroxysmal nocturnal haemo-globinuria, Down's syndrome, and chromosomal breakage syndromes are excluded. Though the myelodysplastic syndromes occur mainly in the elderly;, they have been increasingly recognised in younger patients, including children,3 and after chemo-therapy or radiotherapy for malignant and non-malignant disease.4 Cytopenia is a dominant feature, most patients presenting with anaemia, infection, bruising, or haemorrhage. The liver and the spleen may be enlarged, though not strikingly so except in chronic myelomonocytic leukaemia, where hypertrophy of'the gums, infiltrative skin lesions, lymphadenopathy, and, rarely, serous effusions also occur.5 6 Typically there is a combination of anaemia, neutropenia, and thrombocytopenia, though-in chronic myelomonocytic leukaemia there is a characteristic monocytosis and neutro-philia. Anaemia, usually macrocytic despite the absence of vitamin B12 or folic acid deficiency, is accompanied by a range of red cell abnormalities and hyposegmented (pseudo-Pelger) hypogranular neutrophils. The bone marrow reflects ineffective haemopoiesis'and shows characteristic morphological abnormalities of all cell lines. These features are mirrored by functional defects of the neutrophils and platelets, which contribute to the risk of infection and bleedmig.78 A variety of non-specific epiphenomena occur, including quantitative red cell enzyme abnormalities, low neutrophil alkaline phosphatase activity, raised fetal haemo-globin concentrations, altered expression of blood group antigens, and, rarely, a positive Ham's-test. Serum and urinary lysozyme activities are raised in chronic myelomono-cytic leukaemia. Non-random chromosome abnormalities occur in up to 79% of cases.9 Some of these have specific clinical correlations. For example, deletion of the long arm (q) of chromosome 5 is associated with a syndrome seen mainly in elderly women characterised by macrocytic anaemia, a normal or high platelet count, and long survival.'0 Recently myelodysplastic syndromes have been shown to coexist on occasions with proliferative disorders of B or T lymphoid cells, perhaps indicating involvement …