Toxic etiology of aplastic anemia. The Cooperative Study Group for Aplastic and Refractory Anemias.

In this retrospective investigation into the possible causes of aplastic anemia, the charts of 360 patients with primary or secondary aplastic anemia were analyzed for clinical history, proof of diagnosis, possible etiology, and prognostic criteria. During the period of the study, the proportion of cases of aplastic anemia due to chloramphenicol, benzene, butazone, and sulfonamides decreased, whereas the proportion due to gold salts, penicillamine, amidopyrine, and trimethoprim-sulfamethoxazole increased. No case of secondary aplastic anemia in recent years could be attributed with certainty to thiamphenicol; one possible case of thiamphenicol-induced aplastic anemia could have been due to exposure to other chemicals known to cause aplastic anemia. The disease course and mortality rate for secondary aplastic anemia are similar to those for primary aplastic anemia. The results of this study show the need for more careful investigation into the causes of all cases of aplastic anemia attributed to toxic agents or environmental factors.