Aplastic anemia associated with antithyroid drugs.

Prognosis in aplastic anemia is usually linked to the degree of hypoplasia in the bone marrow and pancytopenia in the blood. The authors were, therefore, intrigued when a patient with methimazole-associated aplastic anemia who satisfied criteria for severe disease recovered rapidly and completely once her drug was withdrawn. Review of the English language literature revealed ten fully documented cases of aplastic anemia associated with use of the antithyroid drugs methimazole, carbimazole, and propylthiouracil. Analysis of the ten and of an eleventh case presented here indicated that the disorder is typically characterized by severe pancytopenia and profound marrow hypoplasia, yet surprisingly good prognosis, ie, minimum survival of more than 70% with partial or complete recovery from symptoms and cytopenias in survivors within 2-5 weeks. The only deaths, both in the 1950s, were from brain hemorrhage in patients who were not transfused with platelets. The discrepancy between the clinical and laboratory severity of antithyroid drug-associated aplasia, on the one hand, and its relatively good prognosis and short term course, on the other, should be kept in mind when considering these patients for bone marrow transplantation or for therapy with antithymocyte globulin.