All issues > Volume 51(5); 2008

Case Report

Korean J Pediatr. 2008;51(5):546-550. Published online May 15, 2008.

A case of two sisters births from mother with phenylketonuria lacking mental retardation

Chang-Seok CS Ki¹, Jin Kyung JK Kim²

¹Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sung Kyun Kwan University School of Medicine, Korea
²Department of Pediatrics, College of Medicine, Daegu Catholic University, Daegu, Korea

Correspondence Jin Kyung JK Kim ,Email: kimjk@cu.ac.kr

Abstract

In this untreated classic phenylketonuria (PKU) case, mental retardation is severe; however, there have been individuals­like the mother of this case­who have escaped mental retardation and all the other potential sequelae of phenylketonuria, despite having high blood phenylalanine levels, and very poor dietary control. It appears that they have nearly normal brain phenylalanine levels despite high blood phenylalanine (Phe) levels. A number of studies have now demonstrated considerable variability in blood vs. brain phenylalanine levels in phenylketonuria patients. Outcome of phenylketonuria appears to be related to brain phenylalanine levels. We report a case of "undiagnosed" maternal phenylketonuria syndrome. A female infant had low birth weight (2,400 g) with microcephaly. We examined her family and discovered that her mother was an undiagnosed phenylketonuria patient with a borderline intelligence quotient (IQ). The infant's sister, six years old, was diagnosed with phenylketonuria at the age of four years was mentally retarded and had received an operation for cleft lip and palate. the sister had also had a low birth weight (2,300 g). Her sister and mother were compound heterozygotes (mother: R243Q/Y325X; sister: Y325X/P407S). The infant and father were heterozygous carriers (baby: R243Q/－; father: P407S/－).

Keywords :Phenylalanine; Phenylalanine hydroxylase; Phenylketonuria; Maternal phenylketonuria syndrome