Normal bone marrow karyotype in acute leukemia or myelodysplasia following rheumatoid arthritis?

Cytogenetic analyses by means of trypsin-Giemsa banding technique were performed on bone marrow cells from a total of 12 patients--nine with acute nonlymphocytic leukemia and three with myelodysplastic syndrome--and a history of rheumatoid arthritis. Clonal chromosomal abnormalities were identified in two patients with previous exposure to petroleum products, and radiation therapy for a malignant tumor, respectively; one additional patient had a loss of the Y chromosome as the sole aberration. All the remaining nine patients had completely normal karyotypes. Seven patients had received treatment for rheumatoid arthritis with mutagenic drugs. Acute nonlymphocytic leukemia or myelodysplastic syndrome secondary to cytotoxic treatment for a previous malignancy display multiple, usually complex, structural and numerical chromosomal abnormalities in the majority of cases. The contrasting findings in the present patient series suggest other pathogenetic mechanisms in acute nonlymphocytic leukemia and myelodysplastic syndrome following rheumatoid arthritis.