Acute Basophilic Leukemia: Recent Molecular and Diagnostic Update

Acute basophilic leukemia (ABL) is an uncommon subtype of acute leukemia characterized by clinical signs and symptoms related to hyper-histaminemia. Patients usually present with bone marrow (BM) failure due to the infiltration of BM by the blasts and may or may not have circulating blasts. Myeloid markers such as CD13 and CD33 are expressed by leukemic blasts, which are also positive for CD123, CD203c, and CD11b, but KIT (CD117) and other monocytic markers are usually negative. t(X;6) (p11; q23) translocation resulting in the MYB-GATA1 fusion gene has been seen in sporadic cases of ABL. Early phases of hematopoiesis are characterized by high levels of MYB and low levels of GATA1; as differentiation develops, an inverse regulation occurs, resulting in high levels of GATA1 and low levels of MYB.The translocation t(X;6) produces the MYB-GATA1 fusion gene (p11; q23). In mouse lineage-negative cells, MYB-GATA1 expression commits them to the granulocyte lineage and inhibited differentiation at an early stage. Cells expressing MYB-GATA1 show enhanced expression of markers of immaturity (CD34), granulocytic lineage (CD33 and CD117), and basophilic differentiation (CD203c and FcRI). NTRK1 and IL1RL1 transcription is directly triggered by MYB and MYB-GATA1, resulting in basophilic skewing of the blasts.