Ultrastructural abnormalities of bone marrow erythroblasts in refractory anemia.

Ultrastructural abnormalities of erythroblasts in 30 patients with refractory anemia (RA) according to FAB classification were studied. Nuclear clefts, iron-laden mitochondria, and myelin figures in cytoplasm were most frequently observed. Eleven patients (36.7%) with nuclear clefts of erythroblasts had a higher platelet count and higher incidence of cytogenetic abnormalities linked to poor prognosis than the patients without nuclear clefts. They also had a higher frequency of leukemic transformation and shorter survival than the patients without nuclear clefts. The nuclear clefts of erythroblasts, which are the result of impairment of DNA metabolism or nuclear formation and fusion during mitosis, may be one of the adverse prognostic factors for patients with RA.