This observation is best explained by expression of CD203c on circulating basophil-committed progenitor cells in some of these patients, a hypothesis that was confirmed by the observation that CD203c is also detectable on a subset of CD34+ progenitor cells in the BM and that these CD203c+ basophil-committed progenitor cells are more prevalent in CML patients compared to healthy controls. The gene discussed is CD34; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.