Eosinophil chimerism in the differential diagnosis between DEK-NUP214-positive acute myeloid leukaemia relapse and chronic graft-versus-host disease

Eosinophilia is a rare, recurrent finding in acute myeloid leukaemia (AML). The classic cases include core-binding factor AMLs with chromosome 16 abnormalities and AMLs with rearrangements of the platelet derived growth factor (PDGF) receptor A and B genes ( PDGFRA and PDGFRB ) and the fibroblast growth factor receptor 1 gene ( FGFR1 ). AML with t(6;9)(p23;q24) is a rare entity (0.7%–1.8% of all AMLs), characterised by multilineage dysplasia, basophilia and an unfavourable prognosis.1–3 This cytogenetic alteration leads to the formation of the DEK-NUP214 hybrid protein, and usually presents as a single abnormality, but it can also be associated with a complex karyotype.4 There are currently no descriptions of eosinophilia associated with DEK-NUP214+ AML. We report the case of a 16-year-old male patient who presented with generalised cutaneous pruritus and fever, associated with peripheral blood eosinophilia (absolute count 7830 cells/μL) in August 2010. After ruling out common causes of secondary eosinophilia, the patient was submitted to bone marrow aspiration, which showed erythroid hyperplasia (58.8%) with dyserythropoiesis, eosinophilia (16.4%), dysgranulopoiesis and 9.6% blast cells. These findings were compatible with the diagnosis of AML-M6, according to the French–American–British classification. A cytogenetic study showed the presence of t(6;9) (p23;q34) as the sole anomaly. Fluorescence in-situ hybridisation (FISH) was negative for inv(16), and molecular studies showed wild-type sequences for the fms-related tyrosine kinase 3 ( FLT3 ) and nucleophosmin ( NPM1 ). FISH was also negative for PDGFRA rearrangement. The patient was treated with two cycles of cytarabine-based chemotherapy, achieving haematological remission; nevertheless, peripheral …