Chromosomal aneuploidy in a patient with hypereosinophilic syndrome. Evidence for a malignant disease.

A patient with rapidly fatal hypereosinophilic syndrome and a bone marrow chromosomal abnormality, 49,XYY,t(3:5),+8,+mar, is described. Scanning and transmission electron microscopy of eosinophils failed to reveal any significant abnormalities. Previous cytogenetic data on patients with hypereosinophilic syndrome have been deficient in that few studies have been performed with banding technics. These technics may help in the classification of hypereosinophilic syndrome and predict which patients will have a rapidly fatal course.