Chronic Eosinophilic Leukaemia Associated with JAK2 Exon 13 Insertion/Deletion Mutations

Abstract

Chronic eosinophilic leukaemia, not otherwise specified (CEL, NOS), is a diagnosis of exclusion made in cases in which there is clonal eosinophilia but an absence of genetic aberrations that define other disease subtypes. There is a need for further characterization of these cases in order to inform risk stratification and management. The importance of <i>JAK2</i> mutations in myeloproliferative neoplasms (MPN) as a whole is well established, although their role specifically in eosinophilic disorders is less clear, with only a minority of cases demonstrating <i>JAK2</i> abnormalities. Here, we report 2 cases with an exon 13 insertion-deletion (indel) mutation in <i>JAK2:</i> one with CEL-NOS and the second with an unspecified eosinophilic disorder. <i>JAK2</i> indels were not detected in a screen of suspected MPN cases (<i>n</i> = 592) without eosinophilia that tested negative for common MPN driver mutations. Our findings thus provide further evidence for a specific association between this rare mutation and clonal eosinophilic disorders.