A case of chronic aneosinocytosis.

A 59-year-old woman, after complete recovery from an episode of drug-induced agranulocytosis, was found to sustain a chronic absence of recognizable mature and immature eosinophils in blood and bone marrow during a follow-up period of 8 years. Her bone marrow and peripheral blood cells cultured in vitro were able to produce normal numbers of eosinophil colonies. The present disorder was thus not caused by a lack of EO-CFU-C, nor by a defect in EO-CSA, nor by an immunologically mediated mechanism acting on mature or immature eosinophils or on EO-CSA producing cells. It is suggested that the marrow was not able to differentiate normally along the eosinophil pathway, possibly owing to a microenvironmental defect or, less likely, an intrinsic stem cell defect.