Peripheral acute leukemia: high peripheral but low-marrow blast count.

We report five patients who had greater than 30% peripheral blasts and less than 30% marrow blasts. By the current standards these cases would be classified as myelodysplastic syndrome. Four of five patients progressed to acute leukemia within approximately 1 1/2 months of developing greater than 30% peripheral blasts. Two of these four patients had evidence of acute leukemia by criteria other than marrow involvement at the time of presentation: one patient had evidence of multifocal dermal involvement; and the other patient had a cytogenetic abnormality, t(8;21), found predominantly in acute leukemia. The fifth patient developed acute leukemia 2 years after initial presentation with greater than 30% peripheral blasts. Although our series of patients is small, it does suggest that patients who have greater than 30% peripheral blasts should be considered an acute leukemia, even with less than 30% marrow blasts.