Trisomy 5 in Ph+ chronic myeloid leukemia in association with megakaryocytosis.

A patient with a megakaryocytosis associated with a Philadelphia chromosome-positive chronic myeloid leukemia (CML) was found to have a trisomy of chromosome five. To our knowledge, this is the first case of trisomy 5 associated with a Ph + CML, particularly one with a megakaryocytosis. The trisomy 5 may be associated with the resistance to cytostatic drugs found in this patient.