Neonatal vitamin K administration and in vivo somatic mutation.

The glycophorin A (GPA) mutation assay was used to examine the risk of in vivo somatic mutation in infants following neonatal administration of vitamin K. The assay assesses damage to erythroid stem cells by measuring the frequency of NO and NN variant red cells of MN blood group heterozygotes using FACS analysis. Blood samples were obtained from 178 infants aged between 10 and 183 days. Twenty-six children were excluded from study having received a blood transfusion. Sixty-four of the remaining 152 infants were of the MN phenotype, samples from whom were analysed using the assay system, providing the first data of NO and NN variant frequencies (vfs) in children aged less than 1 year. Twenty of these 64 infants received vitamin K orally (group A), 17 intramuscularly (group B) and 25 intravenously (group C). Results were compared with those from a reference population of children aged 1-15 years. There were no significant differences in NO, NN and total vf between any of groups A, B and C. For all groups both NO and total vf were significantly lower than those for the control population. This result is of some interest and clearly warrants further investigation. NN and total vfs were greater than the 95th percentile for the pooled data from groups A, B and C in three instances, one in each group. It was thus not possible to demonstrate an association between the route of vitamin K administration and an increase in mutation at the GPA locus.