Myelodysplastic Syndrome with Hypereosinophilia and a Nonrandom Chromosomal Abnormality dic(1;7): Confirmation of Eosinophil Clonal Involvement by Fluorescence In Situ Hybridization

We report a case of de novo myelodysplastic syndrome (MDS) with hypereosinophilia and dic(1;7) in which eosinophil clonal involvement was confirmed by fluorescence in situ hybridization. There have been two previous reports in the literature of eosinophilic MDS with dic(1;7) or t(1;7) in which eosinophil clonality was demonstrated. The specific breakpoints on chromosomes 1 and 7 differ in the three cases, making it difficult to implicate disruption of a single gene as causative; nevertheless, the nonrandom occurrence of t(1;7) or dic(1;7) with malignant eosinophilic proliferations suggests that this chromosomal rearrangement is involved in the etiology of the disease.