Paternal phenylketonuria

Infants of mothers with phenylketonuria (PKU), an inborn error of metabolism, may develop microcephaly, an abnormal smallness of the head; mental retardation; and congenital heart defects. They also tend to have low birthweight. There is limited information about the development of abnormalities in children of fathers with PKU. One study showed that men with PKU had lower sperm counts and reduced semen volume, suggesting a limited reproductive potential. However, men with PKU are capable of fathering children, and these children have a lower frequency of abnormalities than children of mothers with PKU. Previous studies examining the outcome of children of fathers with PKU have produced inconsistent results. Six families of fathers with PKU are described and include nine offspring without PKU. The results suggest that paternal PKU does not adversely affect the outcome of offspring. None of the nine children had microcephaly, low birthweight, or congenital heart disease. In addition, the study showed that men with PKU have normal fertility. The greater frequency of abnormalities associated with maternal PKU may result from the transfer of biochemical abnormalities from the mother to the fetus during pregnancy, not from damage to the fertilized egg caused by genetic factors. (Consumer Summary produced by Reliance Medical Information, Inc.)