Disappearance of Chromosomal Abnormalities in Megaloblastic Anaemia after Treatment

Chromosome changes were studied in three patients with megaloblastic anaemia before and after treatment with vitamin B12. Chromosome No. 1 in one megaloblastic marrow showed a mean length 25% greater than normal. In another patient studied after conversion to normoblastic erythropoiesis, the mean length of the No. 1 chromosome was normal. Giant chromosomes seem to be characteristic of megaloblastic bone marrow cells. They represent a phenomenon reversible by treatment. The effect of treatment with vitamin B12 on the number of bone marrow cells with chromosome breaks was followed in one patient. A drastic decrease from 40 to 10% was observed 3–5 days after giving vitamin B12, coinciding with the reticulocyte response. In another patient blood transfusions seemed to lower the number of cells with breaks, no reticulocyte response was noted, and the marrow remained megaloblastic.