Hematologic abnormalities in children with Down syndrome.

We compared the hematologic parameters of 18 otherwise healthy children with Down syndrome (DS) in the age range of 2-6 years to those of 18 healthy non-DS controls matched for age and gender. The children with DS had MCVs and hematocrits increased significantly compared to controls and decreased WBCs compared to controls; 66% of the children with DS compared to 11% of non-DS controls had MCVs greater than the 97th percentile for age (P < 0.0001); the mean MCVs were 86.9 and 80.6, respectively. Although hematocrits were within normal limits for age for all DS and non-DS subjects, the DS patients had significantly higher hematocrits (39.1% vs. 36.9%, P < 0.014). We also found that 33% of the children had WBCs < 5% for age compared to 6% of controls. To determine whether folate deficiency contributed to these observations, we measured serum and RBC folate concentrations: these were not significantly different between the 2 groups. We conclude that macrocytosis and leukopenia are common in children with DS.