Abstract
Bone marrows from 23 patients with haemopoietic dysplasia were cultured in agar‐gel and the patients were followed for at least 6 months after culture. The incidence of colonies, microclusters and macroclusters and the colony to cluster and microcluster to macrocluster ratios were compared to those of a control group. In the control patients a normal wide range of colonies and clusters was observed and colony growth correlated with cluster growth. About half of the dysplastic patients showed a normal growth pattern and ran a stable and benign course. The other dysplastic patients had defective colony growth, a low colony to cluster ratio, an increased microcluster to macrocluster ratio and a deficient macrocluster growth early in culture. These patients more often presented with cytopenia and had a malignant course with increasing bone marrow dysplasia and a frequent need of blood transfusions. Some patients died of cytopenia or transformed into acute leukaemia.The bone marrow cultures of haemopoietic dysplasia did not predict the short term (within 6 months) risk of leukaemia transformation. However, the results indicate that examination of culture growth can be used to differentiate stable and benign patients from those in whom clonal abnormalities may suggest a progressive and malignant course.