Sapropterin Dihydrochloride (6R-BH4) and Maternal Phenylketonuria Two Case Studies

Abstract

The dietary treatment of phenylketonuria (PKU) is a success story. However, the Maternal PKU Collaborative Study reported microcephaly, congenital heart defects, facial dysmorphology, and intrauterine and postnatal growth retardation in the offspring of women with blood phenylalanine (phe) concentrations >600 µ mol/L. Dietary control of phe during pregnancy is extremely difficult for many women because of hyper-emesis gravidarum, intolerance of the medical food products, and inability/ refusal to follow dietary recommendations. The authors report 2 case studies using 6R-BH4 along with the phere-stricted diet. Two individuals received 6R-BH4 shortly before conception and throughout the pregnancy. A pherestricted diet was followed with blood phe analysis obtained weekly. Interim plasma amino acids, complete metabolic panels, complete blood counts, and analyses for nutritional deficiencies were also obtained during the pregnancy. Both individuals maintained blood phe concentrations within the recommended range (120-360 µ mol/L) nearly all through the pregnancy with a small percentage outside of recommendations. One participant showed deficiencies in vitamin D and zinc and received supplementation. Both were able to increase natural protein as the pregnancy progressed. Ingestion of the 6R-BH4 was well tolerated. Both gave birth to healthy normal infants. In these case studies, both babies’ birth measurements were in the normal range, and the 6R-BH4 had no adverse effects.