Macrocytosis in Down syndrome.

The mean corpuscular volume of erythrocytes in persons with Down syndrome is larger than normal in the absence of anemia. The mean mean corpuscular volume among our 61 subjects with trisomy 21 was 99.08 fl (range = 90 to 107). Red blood cell survival half-time was substantially shorter than normal in many of these patients. These findings suggest that erythrocytes have a younger mean age in persons with Down syndrome. The increased red blood cell turnover in this population may indicate an accelerated aging process of red blood cells.