Clonality of chronic neutrophilic leukemia.

Kwong and Cheng’ recently reported a case of chronic neutrophilic leukemia (CNL) with absence of Philadelphia (Ph) chromosome and no bcr rearrangement. They showed the clonal nature of CNL by the methylation status of the X-linked hypoxanthine phosphoribosyl transferase. (HPRT) gene. The clonal myeloproliferative nature of CNL was first documented in our report of a case of polycythemia vera (PV) terminating in CNL.’ Similar associations have been published since then,’s4 confirming a clinical connection between CNL and the well-recognized clonal myeloproliferative disorder, PV. The lack of bcr rearrangement in CNL was first demonstrated by well before the case referred to by Kwong and Cheng,’ thus confirming that CNL, which can be mistaken for Ph-negative chronic myeloid leukemia, is a different myeloproliferative disorder.