Polycythaemia rubra vera transforming to acute lymphoblastic leukaemia.

Two patients who developed acute lymphoblastic leukaemia following polycythaemia rubra vera (PRV) are described. In both cases the diagnosis was made using cytochemistry and immunological markers. One patient's cells marked as T-cell acute lymphoblastic leukaemia (T-ALL), the other as unclassified (null) ALL. These cases support the concept that PRV is a stem cell disorder.