Low increase in phenylalanine tolerance during pregnancies in PKU woman with high prepregnancy BMI and postconceptional initiation of diet: A case report

Background: Women with untreated phenylketonuria (PKU) are at an increased risk to have offspring with multiple abnormalities due to teratogenic effects of hyperphenylalaninaemia. Treatment goals include blood phenylalanine concentrations between 120 and 360 µmol/L, however, there are limited pieces of evidence for the practical management of pregnant PKU patient and prediction of phenylalanine tolerance changes during a course of pregnancy. Case: We report the case of a mother with classical PKU (p.R408W/p.R408W) and the course of her two pregnancies with low phenylalanine tolerance increase (347mg and 227mg) despite the rewarding collaboration with a nutritionist. Conclusion: This case report does not confirm the observation that a very low phenylalanine tolerance increase in pregnancy of PKU patient is a marker of coexisting PKU-affection in fetus.