Erythropoiesis in myelofibrosis with myeloid metaplasia: recognition of different classes of patients by erythrokinetics.

A quantitative assessment of erythropoiesis was performed by means of a mathematical model of iron kinetics in 26 patients with myelofibrosis with myeloid metaplasia (MMM). A direct relationship between total erythropoiesis and red cell volume was revealed. This 'inverse' characteristic of erythropoietic control was the best marker of the proliferative nature of the disease. Three classes of patients were singled out by means of a cluster analysis of the erythrokinetic parameters. In class I (11 patients) the red cell volume was above the predicted normal in all but two patients. Erythropoiesis was sustained at 5--10 times the normal levels with a high degree of ineffective erythropoiesis. A fairly constant absence of erythroid activity over the sacral marrow was demonstrated. In class II most of the 12 patients had a decreased red cell volume. Erythropoiesis was sustained at 2--4 times the normal level with a high degree of peripheral haemolysis. Erythroid activity was recognized over the sacral area in all but two patients. The three patients of class III showed a pattern of erythroid failure and had the worst prognosis. It is suggested that these classes represent separate disease forms of MMM.