FIP1L1-PDGFRA positive chronic eosinophilic leukemia in Tunisian patients.

Abstract Hypereosinophilic syndromes (HES) are a heterogenous group of rare disorders characterized by sustained and otherwise unexplained overproduction of eosinophils with organ involvement and consecutive dysfunction. Detection of the FIP1L1–PDGFRA fusion gene or the corresponding cryptic 4q12 deletion in HES supports the diagnosis of chronic eosinophilic leukemia (CEL) and provides a molecular explanation for the pathogenesis of this disorder. We screened seven Tunisian patients fulfilling the WHO criteria of HES for the presence of the FIP1L1–PDGFRA fusion gene using nested reverse transcription polymerase chain reaction on peripheral blood samples. Four of the seven patients were positive for this fusion gene. Sequence analysis revealed a substantial heterogeneity of the fusion transcripts due to the involvement of several FIP1L1 exons. All patients were male. The median age at diagnosis was 24 years (range, 18–50); one patient had a history of hypereosinophilia of more than 10 years. Two patients had clinically important and symptomatic eosinophilic endomyocardial disease with thrombotic events. Splenomegaly was constant in FIP1L1–PDGFRA positive CEL but not in the other HES patients (only 1/3).