Many women with PKU are well-informed about the risks of maternal PKU but there are several barriers to achieving satisfactory metabolic control before and during pregnancy.
A 31 year old MPKU female with classical PKU (mutations P281L/P281L), diagnosed by newborn screening, had a lifelong history of poor metabolic control.
This experience and review of the literature indicates that the residual liver phenylalanine hydroxylase activity of a nonphenylketonuric fetus offers little or no protection from damage in untreated maternal PKU.
Maternal phenylketonuria syndrome in cousins caused by mild, unrecognized phenylketonuria in their mothers homozygous for the phenylalanine hydroxylase Arg-261-Gln mutation.
The exact mechanism of fetal damage in maternal phenylketonuria (PKU) is uncertain and although the fetus is heterozygotic for the gene coding for phenylalanine hydroxylase its immature hepatic enzyme system may be the reason for its inability to deal adequately with transplacental phenylalanine uptake.