Dual presentation of polycythaemia vera and lymphatic leukaemia.

A case is described in which polycythaemia vera was found to co-exist with chronic lymphatic leukaemia at the time of presentation. This case can be added to five other reported cases of an association between polycythaemia vera and well-differentiated lymphocytic neoplasia, and adds further emphasis to the tendency for dual presentation, which has now occurred in all but one of these cases. One explanation is that the association is due to chance, but the tendency for dual presentation raises the possibility that the overall picture reflects neoplastic involvement of stem cells with capacity to differentiate into the lymphoid as well as the erythroid, myeloid and megakaryocytic series.