Erythroid differentiation blocked by the expression of PML‐RARα has been demonstrated in several cell models.6, 10 For example, expression of PML‐RARα in CD34+/Lin‐ cells enables normal haematopoietic progenitor/stem cells to reach the promyelocytic level of differentiation but not to go further along the erythroid or the thrombocytic lineage, even if cells are cultivated in an adequate cytokine cocktail.6 Disrupted erythroid differentiation by the oncogenic fusion proteins is also associated with the pathogenesis of t(8;21) AML. The gene discussed is CD34; the disease is acute myeloid leukemia.