Although eosinophilia has been reported as a side effect of purine analogue
s, there is no report on fludarabine-induced eosinophilia in chronic lympho
cytic leukemia (CLL). During chemotherapy with fludarabine and cyclophospha
mide, we observed two cases of significant eosinophilia. A 67-year-old pati
ent with CLL developed bone marrow and peripheral blood eosinophilia up to
7.9 x 10(9)/l, the highest eosinophil count ever, reported during treatment
with a purine analogue. The eosinophilia persisted for 33 days. Another pa
tient developed bone marrow eosinophilia without eosinophilia in the periph
eral blood. These are the first documented cases of fludarabine-induced eos
inophilia in CLL, and this side effect may conceivably be more common than
previously recognized.