Platelet peroxidase-like activity detected in mature erythroblasts from a patient with pernicious anemia.

We report a case of pernicious anemia in which the possession of platelet peroxidase (PPO)-like activity was proved in its erythroblasts. PPO-positive cells were found in a distinct minor population of hemoglobinized (as a mean of differentiated) erythroid cells in the bone marrow before treatment, but these cells disappeared following therapy with vitamin B12. The present report is considered to be the first case to identify PPO-like activity in mature erythroblasts from the nonmalignant clone. The existence of PPO in erythroid lineage in cases with pernicious anemia is discussed.