Macrocytosis in Down's syndrome and during long-term anticonvulsant therapy.

In a group of non-anaemic mentally retarded patients a significant increase in mean red cell volume has been demonstrated in epileptic patients being treated with anticonvulsants. The possible sites of interference of anticonvulsants with folate activity in the body, and problems associated with folic acid supplements during anticonvulsant therapy, are discussed. During the survey it was confirmed that the mean red cell volume is abnormally increased in many cases of Down's syndrome.