A new hematologic syndrome with a distinct karyotype: the 5 q--chromosome.

Five patients, four women and one man, age 32-8- yr, all whites, had refractory anemia with the same abnormal bone marrow karyotype, i.e., a partial deletion of the long arm of the No. 5 chromosome. The hematologic syndrome was practically the same in these five cases. Examination of the blood revealed a moderate to severe, generally macrocytic anemia with slight leukopenia but normal or elevated platelet count. The bone marrow showed a depressed erythroid series and some abnormalities of the granulocytic series with an occasional excess of myeloblasts. Most of the megakaryocytes had a nonlobulated nucleus. These features, as well as cytogenetic, electron microscopic, isotopic, platelet function, and immunologic studies, are described in detail. The relationship of this newly established syndrome to other hematologic diseases is discussed. The syndrome constitutes another example of the association between a specific abnormal chromosome and a distinct hematologic disorder.