Severe Prolonged Cough as Presenting Manifestation of FIP1L1-PDGFRA+ Chronic Eosinophilic Leukaemia: A Widely Ignored Association.

Chronic eosinophilic leukaemia associated with the FIP1L1-PDGFRA fusion gene (F/P+ CEL) is a rare cause of marked persistent hypereosinophilia, arising almost exclusively in male patients. Clinical presentations are heterogeneous with a higher incidence of eosinophil-mediated cardiomyopathy than in other hypereosinophilic syndrome variants. Features of chronic myeloproliferative disease are often present, including splenomegaly and elevated serum vitamin B12 levels. The diagnosis is made by fluorescence in situ hybridization (FISH) showing the deletion of the CHIC2 locus and/or RT-PCR showing the FIP1L1-PDGFRA fusion transcript. Treatment with imatinib mesylate, a tyrosine kinase inhibitor, results in rapid and complete resolution of hypereosinophilia and associated symptoms, except for those related to sub-endocardial fibrosis that may be irreversible. We report the case of a male patient in whom isolated intractable cough remained the only clinical manifestation of F/P+ CEL for 4 years. Furthermore, eosinophil autofluorescence, an as yet unreported artefact in this setting, precluded the detection of the CHIC2 deletion and further delayed diagnosis, underlining that both FISH and RT-PCR should be performed when this disease is suspected.