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A clinical, cytological and biological study of a 57‐year‐old man with a sideroblastic anaemia is presented. A large population of cells with 47 chromosomes and an extra C chromosome was found in the bone marrow cells but not in skin cells or lymphocytes. The concentration of uracil nucleotides in the bone marrow of the patient was increased. When incubated with 3 H‐thymidine the erythroblasts of the patient's marrow showed a low labelling index, A considerable number of early erythroblasts not incorporating thymidine had an intermediate DNA content indicating an arrest in DNA synthesis. A normal labelling index was recorded for the myelopoietic cells.
Hellström et al. (1971) studied this question.