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

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 JAK2 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 JAK2 abnormalities. Here, we report 2 cases with an exon 13 insertion-deletion (indel) mutation in JAK2: one with CEL-NOS and the second with an unspecified eosinophilic disorder. JAK2 indels were not detected in a screen of suspected MPN cases (n = 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.

How to use Donath-Landsteiner test to diagnose paroxysmal cold haemoglobinuria (PCH).

Paroxysmal cold haemoglobinuria (PCH) accounts for around a third of cases of autoimmune haemolytic anaemia in children. PCH is caused by an autoantibody that fixes complement to red cells at low temperatures and dissociates at warmer temperatures (a biphasic haemolysin), triggering complement-mediated intravascular haemolysis. Named the Donath-Landsteiner (D-L) antibody after its discoverers, it is usually formed in response to infection and demonstrates specificity for the ubiquitous red cell P-antigen. A D-L test can be used to detect the presence of the D-L autoantibody in the patients' serum. Here we discuss the use of the D-L test in identifying PCH in a 2-year-old boy who presented with haemolytic anaemia. A summary of the key information can be found in the infographic.