It has been demonstrated that the anemia is likely due to a block in erythroid differentiation (Hamaguchi et al. 2002), but it is currently unclear whether the leukemia is an indirect result of the anemia, caused by a stimulation in the production of hematopoietic precursors, or whether the rpS19 gene dosage plays a direct role in tumorigenesis. The gene discussed is RPS19; the disease is anemia.